A102630 Numbers n such that no positive number of the form prime(n)-2^k is prime.

1, 2, 31, 35, 54, 67, 68, 74, 97, 109, 126, 134, 140, 151, 155, 165, 168, 171, 181, 205, 244, 251, 256, 260, 274, 275, 276, 285, 298, 328, 330, 341, 352, 368, 376, 389, 405, 413, 417, 421, 430, 444, 447, 450, 451, 463, 471, 481, 495, 509, 510, 516, 522, 526

Offset: 1

Author

Lei Zhou, Jan 20 2005

Keywords

• nonn

Comments

Large primes tested by Primo.

Examples

			Prime(1)=2, 2-2^0=1, not prime.
Prime(31)=127, 127-2^0 through 127-2^6 are nonprime.
		

Links

• Lei Zhou, Between 2^n and primes.

Crossrefs

Cf. A094076, A102631-A102633.

Programs

Mathematica

fQ[n_] := Block[{k = Floor[ Log[2, Prime[n]]], p = Prime[n]}, While[k > -1 && !PrimeQ[p - 2^k], k-- ]; If[k > 0, True, False]]; Select[ Range[ 536], !fQ[ # ] &] (* Robert G. Wilson v, Jan 24 2005 *)

Extensions

More terms from Robert G. Wilson v, Jan 24 2005