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A258781 a(n) is the greatest positive integer k such that lambda(k) <= n where lambda is the Carmichael lambda function (A002322).

%I A258781 #20 Feb 16 2025 08:33:25
%S A258781 2,24,24,240,240,504,504,504,504,504,504,65520,65520,65520,65520,
%T A258781 65520,65520,65520,65520,65520,65520,65520,65520,131040,131040,131040,
%U A258781 131040,131040,131040,171864,171864,171864,171864,171864,171864,138181680,138181680,138181680
%N A258781 a(n) is the greatest positive integer k such that lambda(k) <= n where lambda is the Carmichael lambda function (A002322).
%H A258781 Eric W. Weisstein's mathWorld, <a href="https://mathworld.wolfram.com/ CarmichaelFunction.html">Carmichael Function</a>
%e A258781 a(2)=24 because lambda(24) = 2 and 24 is the greatest number such that lambda(24) <= 2.
%p A258781 with(numtheory):
%p A258781 for n from 1 to 30 do:
%p A258781   ii:=0:
%p A258781    for k from 10^7 by -1 to 1 while(ii=0)do:
%p A258781    if lambda(k)<=n
%p A258781    then
%p A258781    printf(`%d, `,k):ii:=1:
%p A258781    else
%p A258781    fi:
%p A258781   od:
%p A258781 od:
%Y A258781 Cf. A002322, A253215.
%K A258781 nonn
%O A258781 1,1
%A A258781 _Michel Lagneau_, Jun 10 2015
%E A258781 a(36)-a(38) corrected by _Seth A. Troisi_, Nov 22 2015