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 A225882 #27 Oct 08 2022 00:01:04 %S A225882 20,90,336,650,5440,7371,13000,14762,28730,30240,83810,87296,130682, %T A225882 147420,218400,280370,295240,406875,708122,924482,1397760,1875530, %U A225882 2613640,3536000,4881890,4960032,5884851,7856640,7893290,8137500 %N A225882 Numbers k such that core(k) is equal to the sum of the proper square divisors of k, where core(k) = A007913(k). %C A225882 If p is prime and p^2 + 1 squarefree, then p^2*(p^2 + 1) is in the sequence. %H A225882 Giovanni Resta, <a href="/A225882/b225882.txt">Table of n, a(n) for n = 1..282</a> (terms < 5*10^11; first 80 terms from Charles R Greathouse IV) %e A225882 13000 is a term because core(13000) = 130 = 100 + 25 + 4 + 1. %o A225882 (PARI) %o A225882 for(n=2,10^8,if(core(n)==sumdiv(n,d,d*issquare(d)),print(n))) %o A225882 (PARI) ssd(f)=prod(i=1,#f[,1],(f[i,1]^(f[i,2]+2-f[i,2]%2)-1)/(f[i,1]^2-1)) %o A225882 is(n)=my(f=factor(n));prod(i=1,#f[,1],f[i,1]^(f[i,2]%2))==ssd(f) && n>1 \\ _Charles R Greathouse IV_, May 20 2013 %Y A225882 Cf. A007913, A035316, A225880, A225881. %K A225882 nonn %O A225882 1,1 %A A225882 _Antonio Roldán_, May 19 2013