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 A137490 #22 Jul 03 2022 06:46:56
%S A137490 900,1764,2304,4356,4900,6084,6400,10404,11025,12100,12544,12996,
%T A137490 16900,19044,23716,26244,27225,28900,30276,30976,33124,34596,36100,
%U A137490 38025,43264,49284,52900,53361,56644,60516,65025,66564,70756,73984,74529
%N A137490 Numbers with 27 divisors.
%C A137490 Maple implementation: see A030513.
%C A137490 Numbers of the form p^26 (subset of A089081), p^2*q^2*r^2 (like 900, 1764, 4356, squares of A007304) or p^2*q^8 (like 2304, 6400, subset of the squares of A030628) where p, q and r are distinct primes. - _R. J. Mathar_, Mar 01 2010
%H A137490 Vincenzo Librandi, <a href="/A137490/b137490.txt">Table of n, a(n) for n = 1..1000</a>
%F A137490 A000005(a(n)) = 27.
%F A137490 Sum_{n>=1} 1/a(n) = (P(2)^3 + 2*P(6) - 3*P(2)*P(4))/6 + P(2)*P(8) - P(10) + P(26) = 0.00453941..., where P is the prime zeta function. - _Amiram Eldar_, Jul 03 2022
%t A137490 Select[Range[150000],DivisorSigma[0,#]==27&] (* _Vladimir Joseph Stephan Orlovsky_, May 06 2011 *)
%o A137490 (PARI) isA137490(n) = numdiv(n)==27 \\ _Michael B. Porter_, Apr 10 2010
%Y A137490 Cf. A000005, A030513-A030516, A030626, A030627, A030634-A030638, A005179, A003680, A096932, A061286, A061283.
%K A137490 nonn
%O A137490 1,1
%A A137490 _R. J. Mathar_, Apr 22 2008