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A067521 Numbers n such that the square root of n is an integer and a multiple of the sum of the digits of n.

%I A067521 #26 Feb 19 2020 08:53:47
%S A067521 1,81,100,324,400,1296,2025,2401,2704,2916,4225,5184,6400,7744,8100,
%T A067521 10000,11664,12544,20736,26244,32400,33124,36100,39204,40000,46656,
%U A067521 59049,63504,72900,75625,88209,104329,104976,122500,123201,129600
%N A067521 Numbers n such that the square root of n is an integer and a multiple of the sum of the digits of n.
%H A067521 Mehrad Mahmoudian, <a href="/A067521/b067521.txt">Table of n, a(n) for n = 1..10000</a>
%H A067521 Mehrad Mahmoudian, <a href="https://gitlab.com/m.mahmoudian/coding-oeis/-/blob/master/A067521/A067521.R">R code to produce the sequence</a>
%e A067521 18^2=324, 18=2*(3+2+4), so 324 is in the sequence.
%p A067521 dig := X->convert((convert(X,base,10)),`+`); seq(`if`(isprime(i)=false,`if`(i mod dig(i^2)=0,i^2,NULL),NULL),i=1..1000);
%t A067521 Select[Range[500]^2,Divisible[Sqrt[#],Total[IntegerDigits[#]]]&] (* _Harvey P. Dale_, Jul 15 2013 *)
%Y A067521 Subsequence of squares (A000290).
%Y A067521 Cf. A067520 (similar for triangular numbers).
%K A067521 base,easy,nonn
%O A067521 1,2
%A A067521 _Amarnath Murthy_, Feb 14 2002
%E A067521 More terms from _Sascha Kurz_ and Francois Jooste (phukraut(AT)hotmail.com), Mar 18 2002
%E A067521 Definition corrected by _Harvey P. Dale_, Jul 15 2013