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 A145450 #19 Dec 10 2024 05:29:28
%S A145450 1,2,36,108,128,225,288,441,450,600,864,882,1089,1176,1521,1944,2000,
%T A145450 2178,2601,2904,3042,3240,3249,4056,4761,5202,6144,6498,6561,6936,
%U A145450 7569,8649,8664,9522,10000,11760,12321,12696,13122,15129,15138,16641,17298
%N A145450 Numbers k such that k/A000005(k) is a square.
%C A145450 Subsequence of A033950.
%H A145450 Amiram Eldar, <a href="/A145450/b145450.txt">Table of n, a(n) for n = 1..5479</a> (terms below 10^9)
%e A145450 36/A000005(36) = 36/9 = 4 = 2^2, hence 36 is in the sequence.
%t A145450 Select[Range[20000],IntegerQ[Sqrt[#/DivisorSigma[0,#]]]&] (* _Harvey P. Dale_, May 21 2012 *)
%o A145450 (PARI) {m=18000; for(n=1, m, s=sigma(n,0); if(n%s==0&&issquare(n/s), print1(n,",")))}
%Y A145450 Cf. A000005 (sigma_0, number of divisors of n), A033950 (refactorable numbers), A140480 (RMS numbers).
%K A145450 nonn
%O A145450 1,2
%A A145450 _Ctibor O. Zizka_, Oct 10 2008
%E A145450 Edited and extended by _Klaus Brockhaus_, Oct 15 2008