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A181692 The smallest positive m such that 2^m-2^n-1 is prime, or 0 if such an m does not exist. 6
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

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

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 *)

PROG

(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

CROSSREFS

Cf. A096502.

Sequence in context: A093003 A118096 A296440 * A145806 A100989 A188215

Adjacent sequences:  A181689 A181690 A181691 * A181693 A181694 A181695

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Nov 05 2010

EXTENSIONS

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

STATUS

approved

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Last modified October 27 23:26 EDT 2020. Contains 338047 sequences. (Running on oeis4.)