A081504 Numbers n such that there are no primes of the form 2^n+2^i+1 for 0

8, 25, 32, 40, 43, 48, 56, 58, 64, 96, 104, 112, 120, 128, 134, 140, 145, 152, 160, 176, 185, 192, 208, 212, 224, 235, 240, 244, 248, 252, 256, 264, 272, 280, 286, 288, 292, 302, 304, 308, 320, 326, 332, 348, 356, 360, 384, 392, 394, 400, 416, 418, 432, 448

Offset: 1

Author

Ralf Stephan, Apr 21 2003

Keywords

• nonn

Comments

There seem to be no such numbers (bit sizes) such that any 4-bit or 5-bit number is composite, up to n around 200.

Links

• T. D. Noe, Table of n, a(n) for n=1..265

Crossrefs

Cf. A081091, A081092.

Programs

PARI

for(n=2, 1000, f=0; for(i=1, n-1, t=2^n+2^i+1;  if(isprime(t), f=1; break)); if(!f, print1(n", ")))