A015906 First k>n such that k | n^k + n.

1, 2, 6, 4, 10, 6, 14, 8, 12, 10, 22, 12, 15, 14, 30, 16, 34, 18, 38, 20, 28, 22, 46, 24, 28, 26, 54, 28, 35, 30, 51, 32, 44, 34, 70, 36, 52, 38, 78, 40, 70, 42, 86, 44, 60, 46, 94, 48, 56, 50, 66, 52, 106, 54, 66, 56, 76, 58, 118, 60, 85, 62, 66, 64, 80, 66, 134, 68

Offset: 0

Author

Robert G. Wilson v

Keywords

• nonn
• look

Links

• Robert Israel, Table of n, a(n) for n = 0..10000

Programs

Maple

f:= proc(n) local k;
  for k from n+1 do
    if n &^k + n mod k = 0 then return k fi
  od
end proc:
map(f, [$0..100]); # Robert Israel, Sep 13 2018

Mathematica

fk[n_]:=Module[{k=n+1},While[!Divisible[n^k+n,k],k++];k]; Array[fk,70,0] (* Harvey P. Dale, Jan 28 2019 *)

Formula

a(n)=n+1 if n is odd. a(n) <= 2n+2. - Robert Israel, Sep 13 2018

Extensions

a(0)=1 and a(1)=2 inserted by Robert Israel, Sep 13 2018