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 A219793 #8 Nov 30 2012 18:41:49
%S A219793 1,1,3,3,5,3,7,5,7,5,11,5,13,7,32,32,17,7,19,32,13,11,23,32,25,13,19,
%T A219793 13,29,32,31,17,25,17,224,13,37,19,224,17,41,13,43,25,224,23,47,17,43,
%U A219793 25,128,224,53,19,41,224,37,29,59,17,61,31,37,128,119,25
%N A219793 Least k such that phi(n) = lambda(k), or 0 if there is no such k.
%C A219793 lambda(n) is the Carmichael lambda function A002322. For n <10000, it appears that a(n) = 0 for n = 2047, 4094, 6141, 6533, 8119, 8188, 9637. if a(n) = p is a prime greater than 2, then n belongs to the finite set {p, p1, p2, ...., pk} that is a subsequence of A032447 (see the array with characteristic rows in the example of A032447), for example : a(n) = 3 for n = 3, 4, 6; a(n) = 5 for n = 5, 8, 10, 12; a(n) = 7 for n = 7, 9, 14, 18, 15, 16, 20, 24, 30; a(n) = 11 for n = 11, 22; a(n) = 13 for n = 13, 21, 26, 28, 36, 42; a(n) = 17 for n = 17, 32, 34, 40, 48, 60.
%H A219793 Michel Lagneau, <a href="/A219793/b219793.txt">Table of n, a(n) for n = 1..10000</a>
%e A219793 a(6) = 3 because phi(6) = lambda(3) = 2.
%p A219793 with(numtheory): for n from 1 to 100 do: ii:=0:for k from 1 to 10^6 while(ii=0) do:if phi(n)=lambda(k) then ii:=1: printf(`%d, `,k):else fi:od:if ii=0 then printf(`%d, `,0): else fi:od:
%t A219793 Table[k=0; While[!EulerPhi[n] == CarmichaelLambda[k], k++]; k, {n, 100}] (* program will go into an infinite loop at n = 2047 *)
%Y A219793 Cf. A002322, A032447, A141162, A143407.
%K A219793 nonn
%O A219793 1,3
%A A219793 _Michel Lagneau_, Nov 28 2012