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 A180090 #27 Feb 18 2023 10:25:05 %S A180090 81,343,400,1705636,3648100,13645088,25992000,26680500,29184800, %T A180090 80802000,110215125,178054848,180093375,213444000,310144500,408632609, %U A180090 575664500,1055340196,1120504500,1476326929,1667329664,2066544500 %N A180090 Sigma-powerful numbers: powerful numbers n such that sigma(n) is also powerful. An incomplete version of A337045. %C A180090 The list is not exhaustive since the search was restricted to sigma(p^k) such that p<1728 and all powers k such that all primes in the factorization of sigma(p^k) are also less than 1728. %H A180090 Walter A. Kehowski, <a href="/A180090/b180090.txt">Table of n, a(n) for n = 1..1536</a> %H A180090 Walter A. Kehowski, <a href="http://web.gccaz.edu/~walof42631/Sigma-powerful-numbers.html">Sigma-powerful numbers</a> %e A180090 sigma(3^4)=11^2, sigma(7^3)=2^4*5^2, sigma(2^4*5^2)=31^2, sigma(2^2*653^2)=7^2*13^2*19^2. %Y A180090 Cf. A001694, A000203, A128607. %K A180090 dead %O A180090 1,1 %A A180090 _Walter Kehowski_, Aug 09 2010