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 A039781 #11 Feb 25 2021 02:25:38 %S A039781 55,174,183,341,407,1274,5424,6887,18903,22167,27559,53847,66711, %T A039781 68237,77957,78155,91524,132791,133574,138471,149435,191575,220759, %U A039781 274224,339024,413424,432233,493724,505735,543221,684167,694823,703824,711774,747175,883463 %N A039781 Numbers k such that phi(k) is equal to A008473(k+1). %e A039781 phi(174)=56, 175=5^2*7^1, (5+2)*(7+1)=56. %o A039781 (PARI) b(n)=my(f = factor(n)); for (k=1, #f~, f[k, 1] = f[k, 1] + f[k, 2]; f[k, 2] = 1; ); factorback(f); \\ A008473 %o A039781 isok(k) = eulerphi(k) == b(k+1); \\ _Michel Marcus_, Feb 25 2021 %Y A039781 Cf. A000010, A008473. %Y A039781 Cf. A039779, A039780. %K A039781 nonn %O A039781 1,1 %A A039781 _Olivier Gérard_ %E A039781 Title corrected and more terms from _Sean A. Irvine_, Feb 24 2021