Problem 49778. Determine whether a number is a prime self number

Created by ChrisR

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<div style = "text-align: start; line-height: 20.4333px; min-height: 0px; white-space: normal; color: rgb(0, 0, 0); font-family: Menlo, Monaco, Consolas, monospace; font-style: normal; font-size: 14px; font-weight: 400; text-decoration: rgb(0, 0, 0); white-space: normal; "><div style="block-size: 93px; display: block; min-width: 0px; padding-block-start: 0px; padding-top: 0px; perspective-origin: 407px 46.5px; transform-origin: 407px 46.5px; vertical-align: baseline; "><div style="block-size: 63px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 31.5px; text-align: left; transform-origin: 384px 31.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 90.2417px 8.05px; transform-origin: 90.2417px 8.05px; unicode-bidi: normal; "><span style="">Integers can be classified as </span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 31.5167px 8.05px; transform-origin: 31.5167px 8.05px; unicode-bidi: normal; "><span style="font-style: italic; ">generated</span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 39.2833px 8.05px; transform-origin: 39.2833px 8.05px; unicode-bidi: normal; "><span style=""> numbers or </span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 12.8333px 8.05px; transform-origin: 12.8333px 8.05px; unicode-bidi: normal; "><span style="font-style: italic; ">self </span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 209.267px 8.05px; transform-origin: 209.267px 8.05px; unicode-bidi: normal; "><span style="">numbers. A generated number is one that can be expressed as the sum of another number and its digit sum. For example, 15 can be written as 12+(1+2); in other words, 15’s generator is 12. A self number cannot be expressed in this way. </span></span></div><div style="block-size: 21px; font-family: Helvetica, Arial, sans-serif; line-height: 21px; margin-block-end: 9px; margin-block-start: 2px; margin-bottom: 9px; margin-inline-end: 10px; margin-inline-start: 4px; margin-left: 4px; margin-right: 10px; margin-top: 2px; perspective-origin: 384px 10.5px; text-align: left; transform-origin: 384px 10.5px; white-space: pre-wrap; margin-left: 4px; margin-top: 2px; margin-bottom: 9px; margin-right: 10px; "><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 162.458px 8.05px; transform-origin: 162.458px 8.05px; unicode-bidi: normal; "><span style="">Write a function to determine whether a number is a </span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 17.5083px 8.05px; transform-origin: 17.5083px 8.05px; unicode-bidi: normal; "><span style="font-style: italic; ">prime</span></span><span style="block-size: auto; display: inline; margin-block-end: 0px; margin-block-start: 0px; margin-bottom: 0px; margin-inline-end: 0px; margin-inline-start: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; perspective-origin: 42px 8.05px; transform-origin: 42px 8.05px; unicode-bidi: normal; "><span style=""> self number. </span></span></div></div></div>

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26 Solutions
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Last Solution submitted on Sep 09, 2021

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J.R.! Menzinger on 4 Aug 2021

Nice Problem!

but I found remarkable your syntax on test case Nr. 27:
a = arrayfun(@(k) isPrimeSelf(n(k)),1:length(n));

if you use 'arrayfun' you can actually parse the vector directly and you can avoid parsing the indices. The following expression would be more narrow:

a = arrayfun(@isPrimeSelf,n)

ChrisR on 28 Aug 2021 at 18:44

Thanks for pointing that out. I've made the change.

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Problem 49778. Determine whether a number is a prime self number

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Problem 49778. Determine whether a number is a prime self number

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