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A081504
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Numbers n such that there are no primes of the form 2^n+2^i+1, 0<i<n. In binary: all 3-bit numbers with size n+1 are composite.
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5
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| There seem to be no such numbers (bit sizes) such that any 4- or 5-bit number is composite, up to n around 200.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..265
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PROG
| (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", ")))
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CROSSREFS
| Cf. A081091, A081092.
Sequence in context: A122984 A188477 A045860 * A030796 A116086 A042611
Adjacent sequences: A081501 A081502 A081503 * A081505 A081506 A081507
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KEYWORD
| nonn
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AUTHOR
| Ralf Stephan (ralf(AT)ark.in-berlin.de), Apr 21 2003
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