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

5, 13, 17, 139, 173, 179, 467, 907, 1553, 1619, 1867, 2099, 2819, 2957, 3203, 3779, 3947, 4139, 4157, 4283, 4547, 4723, 5483, 6653, 6899, 7013, 7187, 7523, 7643, 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

Offset

1,1

Comments

n such that n-2 is the least k such that n divides A062727(k) = sigma(k^k).

Are all terms prime?

Links

Table of n, a(n) for n=1..58.

Example

17 is in the sequence because 17 divides sigma(15^15) = 821051025385244160 but does not divide sigma(k^k) for any k < 15.

Maple

N:= 20000:
S:= {$1..N}: # to get terms <= N
for kk from 1 while S <> {} do
   v:= numtheory:-sigma(kk^kk);
   F:= select(t -> v mod t = 0, S);
   for nn in F do
     B[nn]:= kk
   od;
   S:= S minus F;
od:
select(t -> B[t]=t-2, [$1..N]);

Crossrefs

Cf. A000203, A062727, A275391.

Sequence in context: A294132 A125146 A051900 * A347475 A294136 A120062

Adjacent sequences: A275797 A275798 A275799 * A275801 A275802 A275803

Keyword

nonn

Author

Robert Israel, Aug 09 2016

Status

approved