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A228878 Happy squares: squares whose trajectory under iteration of sum of squares of digits map includes 1. 1
1, 49, 100, 784, 1444, 1521, 3364, 4096, 4225, 4356, 4900, 7225, 7744, 8281, 9604, 10000, 11025, 12321, 12996, 14641, 15625, 17424, 17956, 22201, 24025, 27225, 27556, 27889, 28561, 29584, 34596, 37636, 42025, 45369, 54289, 55696, 56644, 59049, 59536, 63504 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This was a puzzle mentioned on The Aperiodical website.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Paul Taylor, The Aperiodical: More or Less integer sequence solution revealed (spoilers!)

MATHEMATICA

f[n_] := Total[IntegerDigits[n]^2]; Select[Range[400]^2, NestWhile[f, #, UnsameQ, All] == 1 &]

PROG

(PARI) ssd(n)=n=digits(n); sum(i=1, #n, n[i]^2)

select(n->while(n>6, n=ssd(n)); n==1, vector(1000, i, i^2)) \\ Charles R Greathouse IV, Dec 17 2013

CROSSREFS

Intersection of A000290 and A007770.

Sequence in context: A354342 A230653 A019547 * A067673 A250653 A045253

Adjacent sequences: A228875 A228876 A228877 * A228879 A228880 A228881

KEYWORD

nonn,base

AUTHOR

T. D. Noe, Oct 07 2013

STATUS

approved

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Last modified December 4 23:46 EST 2022. Contains 358572 sequences. (Running on oeis4.)