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 A173942 #18 Dec 02 2019 04:12:26 %S A173942 1,9,18,36,63,72,126,252,504,712,729,1458,1716,2136,2916,2982,3484, %T A173942 3588,4402,5103,5467,5832,7120,7332,8800,9798,9894,10206,10452,11928, %U A173942 12948,13192,13851,14952,17420,17608,17963 %N A173942 Numbers n such that sigma(lambda(n)) = lambda(sigma(n)). %C A173942 Previous name: sigma(lambda(n)) = lambda(sigma(n)) for the sequential application of the sum of divisors of n and Carmichael lambda functions. %C A173942 Numbers n such that A000203(A002322(n))=A002322(A000203(n)). %H A173942 Amiram Eldar, <a href="/A173942/b173942.txt">Table of n, a(n) for n = 1..10000</a> %e A173942 36 is in the sequence because: %e A173942 sigma(lambda(36)) = sigma(6) = 12, %e A173942 lambda(sigma(36)) = lambda(91) = 12. %p A173942 with(numtheory): for n from 1 to 20000 do:if sigma(lambda(n))=lambda(sigma(n))then %p A173942 printf(`%d, `,n):else fi:od: %t A173942 Cases[Range[20000], k_ /; DivisorSigma[1,CarmichaelLambda[k]] == CarmichaelLambda[DivisorSigma[1,k]]] %Y A173942 Cf. A123101, A002322. %K A173942 nonn %O A173942 1,2 %A A173942 _Michel Lagneau_, Nov 26 2010 %E A173942 Name edited by _Michel Marcus_, Mar 18 2016