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A056527
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Numbers where iterated sum of digits of square settles down to a cyclic pattern (in fact 13, 16, 13, 16, ...).
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3
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2, 4, 5, 7, 11, 13, 14, 16, 20, 22, 23, 25, 29, 31, 32, 34, 38, 40, 41, 43, 47, 49, 50, 52, 56, 58, 59, 61, 65, 67, 68, 70, 74, 76, 77, 79, 83, 85, 86, 88, 92, 94, 95, 97, 101, 103, 104, 106, 110, 112, 113, 115, 119, 121, 122, 124, 128, 130, 131, 133, 137, 139, 140
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OFFSET
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1,1
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COMMENTS
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Numbers == 2, 4, 5 or 7 mod 9, i.e. such that n^4 is not congruent to n^2 mod 9
Numbers congruent to {2, 4, 5, 7} mod 9.
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LINKS
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Table of n, a(n) for n=1..63.
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EXAMPLE
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a(1)=2 because iteration starts 2, 4, 7, 13, 16, 13, 16, ....
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CROSSREFS
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Cf. A004159 for sum of digits of square, A056020 where iteration settles to 1, A056020 where iteration settles to 9, also A056528, A056529. Unhappy numbers A031177 deal with iteration of square of sum of digits not settling to a single result.
Sequence in context: A099522 A108464 A128815 * A147991 A033160 A110924
Adjacent sequences: A056524 A056525 A056526 * A056528 A056529 A056530
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KEYWORD
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base,easy,nonn
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AUTHOR
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Henry Bottomley, Jun 19 2000
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STATUS
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approved
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