This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A117678 #24 Oct 23 2015 03:48:58
%S A117678 0,1,4,9,25,100,169,196,225,256,400,529,576,625,676,900,961,1024,1089,
%T A117678 1156,1225,1296,1521,1600,2025,2209,2304,2401,2500,2601,2704,2809,
%U A117678 2916,3025,3136,3481,3600,3844,3969,4096,4225,4356,4489,4900,5041,5184,5329
%N A117678 Squares for which the multiplicative digital root is also a square.
%C A117678 From _Robert Israel_, Oct 22 2015: (Start)
%C A117678 1, 9, and squares in A034048 and A034051.
%C A117678 Are there infinitely many squares in A034051? (End)
%H A117678 Nathaniel Johnston, <a href="/A117678/b117678.txt">Table of n, a(n) for n = 1..5000</a>
%p A117678 A007954 := proc(n) return mul(d, d=convert(n, base, 10)): end: A117678 := proc(n) option remember: local k, m: if(n=1)then return 0:fi: for k from procname(n-1)+1 do m:=k^2: while(length(m)>1)do m:=A007954(m): od: if(m in {0,1,4,9})then return k: fi: od: end: seq(A117678(n)^2, n=1..47); # _Nathaniel Johnston_, May 05 2011
%t A117678 Select[Range[0, 73]^2, IntegerQ@ Sqrt[FixedPoint[Times @@ IntegerDigits@ # &, #] &@ #] &] (* _Michael De Vlieger_, Oct 22 2015 *)
%o A117678 (PARI) t(k) = {while(k>9, k=prod(i=1, #k=digits(k), k[i])); k}
%o A117678 for(n=0, 100, if(issquare(t(n^2)), print1(n^2, ", "))); \\ _Altug Alkan_, Oct 22 2015
%Y A117678 Cf. A000290, A031347, A034048, A034051, A116978.
%K A117678 nonn,easy,base
%O A117678 1,3
%A A117678 Luc Stevens (lms022(AT)yahoo.com), Apr 12 2006
%E A117678 Offset and some terms corrected by _Nathaniel Johnston_, May 05 2011