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 A291638 #11 Sep 02 2017 13:45:12 %S A291638 370440,1704024,3926664,11039112,13854456,21707784,25264008,28375704, %T A291638 40822488,44378712,57862728,59196312,63937944,75051144,79051896, %U A291638 79940952,103500936,107946216,128394504,134766072,162178632,169735608,177737112,191517480,193530168,195221880,196407288,215077464 %N A291638 Numbers n such that psi(n) and sigma(n) both are perfect squares and n is not a squarefree number. %e A291638 370440 = 2^3*3^3*5*7^3 is a term because psi(370440) = 2^2*3^2*7^2*(1+2)*(1+3)*(1+5)*(1+7) = 2^8*3^4*7^2 and sigma(370440) = (1+2+2^2+2^3)*(1+3+3^2+3^3)*(1+5)*(1+7+7^2+7^3) = 2^8*3^2*5^4. %o A291638 (PARI) a001615(n) = my(f=factor(n)); prod(i=1, #f~, f[i, 1]^f[i, 2] + f[i, 1]^(f[i, 2]-1)); %o A291638 isok(n) = !issquarefree(n) && issquare(a001615(n)) && issquare(sigma(n)) \\ after _Charles R Greathouse IV_ at A001615 %Y A291638 Cf. A000203, A001615, A006532, A291167. %K A291638 nonn %O A291638 1,1 %A A291638 _Altug Alkan_, Aug 28 2017