cp's OEIS Frontend

A275800 n such that A275391(n) = n-2.

%I A275800 #7 Aug 09 2016 17:16:16
%S A275800 5,13,17,139,173,179,467,907,1553,1619,1867,2099,2819,2957,3203,3779,
%T A275800 3947,4139,4157,4283,4547,4723,5483,6653,6899,7013,7187,7523,7643,
%U A275800 8147,8387,8563,8573,8753,9533,9587,10589,10853,10883,10979,11003,12107,12227,13037,13229,13829,14243,14549,14699,14867,15299,16217,16547,16649,17387,18443,18587,19259
%N A275800 n such that A275391(n) = n-2.
%C A275800 n such that n-2 is the least k such that n divides A062727(k) = sigma(k^k).
%C A275800 Are all terms prime?
%e A275800 17 is in the sequence because 17 divides sigma(15^15) = 821051025385244160 but does not divide sigma(k^k) for any k < 15.
%p A275800 N:= 20000:
%p A275800 S:= {$1..N}: # to get terms <= N
%p A275800 for kk from 1 while S <> {} do
%p A275800    v:= numtheory:-sigma(kk^kk);
%p A275800    F:= select(t -> v mod t = 0, S);
%p A275800    for nn in F do
%p A275800      B[nn]:= kk
%p A275800    od;
%p A275800    S:= S minus F;
%p A275800 od:
%p A275800 select(t -> B[t]=t-2, [$1..N]);
%Y A275800 Cf. A000203, A062727, A275391.
%K A275800 nonn
%O A275800 1,1
%A A275800 _Robert Israel_, Aug 09 2016