|
Search: id:A081504
|
|
|
| A081504 |
|
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. |
|
+0
5
|
|
| 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; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
There seem to be no such numbers (bit sizes) such that any 4- or 5-bit number is composite, up to n around 200.
|
|
LINKS
|
T. D. Noe, Table of n, a(n) for n=1..265
|
|
PROGRAM
|
(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", ")))
|
|
CROSSREFS
|
Cf. A081091, A081092.
Sequence in context: A103954 A122984 A045860 this_sequence A030796 A116086 A042611
Adjacent sequences: A081501 A081502 A081503 this_sequence A081505 A081506 A081507
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Ralf Stephan (ralf(AT)ark.in-berlin.de), Apr 21 2003
|
|
|
Search completed in 0.002 seconds
|
