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 A067880 #13 Apr 24 2022 06:36:35 %S A067880 2,4,6,10,16,28,78,114,152,165,186,222,224,238,256,402,496,654,704, %T A067880 738,762,834,942,1086,1194,1266,1456,1485,1665,1722,1842,1972,2022, %U A067880 2132,2223,2274,2454,2528,2754,2922,2994,3246,3426,3462,3472,3786,4506,4614 %N A067880 Numbers k such that phi(k) = phi(sigma(k)-k). %H A067880 Amiram Eldar, <a href="/A067880/b067880.txt">Table of n, a(n) for n = 1..10000</a> %t A067880 Select[Range[5000], EulerPhi[#] == EulerPhi[DivisorSigma[1, #] - #] &] (* _Amiram Eldar_, Apr 24 2022 *) %Y A067880 Cf. A000010, A000203, A001065, A006872. %K A067880 easy,nonn %O A067880 1,1 %A A067880 _Benoit Cloitre_, Mar 02 2002