%I
%S 1,49,100,784,1444,1521,3364,4096,4225,4356,4900,7225,7744,8281,9604,
%T 10000,11025,12321,12996,14641,15625,17424,17956,22201,24025,27225,
%U 27556,27889,28561,29584,34596,37636,42025,45369,54289,55696,56644,59049,59536,63504
%N Happy squares: squares whose trajectory under iteration of sum of squares of digits map includes 1.
%C This was a puzzle mentioned on The Aperiodical website.
%H Vincenzo Librandi, <a href="/A228878/b228878.txt">Table of n, a(n) for n = 1..1000</a>
%H Paul Taylor, <a href="http://aperiodical.com/2013/10/moreorlessintegersequencesolutionrevealedspoilers/">The Aperiodical: More or Less integer sequence solution revealed (spoilers!)</a>
%t f[n_] := Total[IntegerDigits[n]^2]; Select[Range[400]^2, NestWhile[f, #, UnsameQ, All] == 1 &]
%o (PARI) ssd(n)=n=digits(n); sum(i=1, #n, n[i]^2)
%o select(n>while(n>6, n=ssd(n)); n==1, vector(1000,i,i^2)) \\ _Charles R Greathouse IV_, Dec 17 2013
%Y Intersection of A000290 and A007770.
%K nonn,base
%O 1,2
%A _T. D. Noe_, Oct 07 2013
