A181692 The smallest positive m such that 2^m-2^n-1 is prime, or 0 if such an m does not exist.

2, 3, 3, 4, 6, 6, 8, 8, 14, 12, 14, 13, 20, 14, 18, 24, 22, 18, 20, 20, 38, 24, 42, 28, 32, 32, 50, 59, 34, 32, 44, 32, 38, 38, 36, 40, 48, 42, 40, 45, 48, 45, 56, 45, 54, 48, 76, 52, 68, 66, 100, 89, 80, 74, 80, 57, 66, 78, 98, 83, 162, 62, 166, 77, 66, 77, 72, 76, 74, 153, 80, 89, 86, 77, 94, 83, 78, 88, 110, 115, 84

Offset: 0

Author

Vladimir Shevelev, Nov 05 2010

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 0..3000

Crossrefs

Cf. A096502.

Programs

Maple

A181692 := proc(n) for m from n to 100000 do if isprime(2^m-2^n-1) then return m; end if; end do: return 0 ; end proc:

Mathematica

m[n_]:=Module[{m=n+1},While[!PrimeQ[2^m-2^n-1],m++];m]
Table[m[i],{i,90}] (* Harvey P. Dale, Dec 18 2010 *)

PARI

for(n=0,80, for(m=n+1,oo, k=2^m-2^n-1; if(isprime(k),print1(m,", "); break))) \\ Hugo Pfoertner, Jan 12 2020

Extensions

a(12) corrected and sequence extended by R. J. Mathar, Nov 17 2010