cp's OEIS Frontend

A141162 Smallest k such that lambda(k) = n, or 0 if there is no such k.

%I A141162 #28 May 13 2018 06:37:48
%S A141162 1,3,0,5,0,7,0,32,0,11,0,13,0,0,0,17,0,19,0,25,0,23,0,224,0,0,0,29,0,
%T A141162 31,0,128,0,0,0,37,0,0,0,41,0,43,0,115,0,47,0,119,0,0,0,53,0,81,0,928,
%U A141162 0,59,0,61,0,0,0,256,0,67,0,0,0,71,0,73,0,0,0,0,0,79,0,187,0,83,0,203,0,0,0,89,0,209,0,235,0,0,0,97,0
%N A141162 Smallest k such that lambda(k) = n, or 0 if there is no such k.
%C A141162 Sequence A002174 gives the n such that a(n) > 0. Removing the zeros from this sequence produces A002396. Note that some n appear only for large k. For example, 728 does not appear until k=49184. See A143407 for the largest k that produces a particular value of the lambda function. See A143408 for the number of times each value occurs. - _T. D. Noe_, Mar 17 2011
%F A141162 a(A002174(n)) = A002396(n).
%e A141162 a(8) = 32 because lambda(32) = 8.
%p A141162 with(numtheory):for k from 1 to 100 do:id:=0:for n from 1 to 1000 while(id=0)
%p A141162   do: if lambda(n) = k then id:=1:printf(`%d, `,n):else fi:od:if id=0 then printf(`%d, `,0):else fi:od:
%t A141162 nn = 100; t = Table[0, {nn}]; Do[c = CarmichaelLambda[k]; If[c <= nn && t[[c]] == 0, t[[c]] = k], {k, 1000}]; t
%Y A141162 Cf. A002174, A002322 (Carmichael lambda function), A002396, A143407, A143408.
%K A141162 nonn
%O A141162 1,2
%A A141162 _Michel Lagneau_, Mar 17 2011