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 A076531 #10 Oct 04 2019 08:48:23 %S A076531 3,203,322,377,644,851,931,1166,1211,1288,1421,1666,1815,1862,2332, %T A076531 2576,3332,3724,4664,4830,5152,6401,6517,6664,7042,7241,7448,9075, %U A076531 9328,9555,9660,9845,9922,9947,10304,10465,11662,11814,11830,12558,12903,13034 %N A076531 Numbers n such that sopf(phi(n)) = phi(sopf(n)), where sopf(x) = sum of the distinct prime factors of x. %H A076531 Amiram Eldar, <a href="/A076531/b076531.txt">Table of n, a(n) for n = 1..10000</a> %e A076531 sopf(phi(203)) = sopf(168) = 12; phi(sopf(203)) = phi(36) = 12 hence 203 is a term of the sequence. %t A076531 p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[3, 10^4], p[EulerPhi[ # ]] == EulerPhi[ p[ # ]] &] %o A076531 (PARI) sopf(n) = my(f=factor(n)); sum(j=1, #f~, f[j, 1]); \\ A008472 %o A076531 isok(n) = eulerphi(sopf(n)) == sopf(eulerphi(n)); \\ _Michel Marcus_, Oct 04 2019 %Y A076531 Cf. A008472, A075565, A075784, A075846, A076525, A076527, A076532, A076533. %K A076531 nonn %O A076531 1,1 %A A076531 _Joseph L. Pe_, Oct 18 2002 %E A076531 Edited and extended by _Ray Chandler_, Feb 13 2005