A133830 Least positive number k<n such that the binary trinomial 1 + 2^n + 2^k is prime, or 0 if there is no such k.

1, 1, 1, 2, 1, 1, 0, 3, 3, 2, 1, 4, 5, 1, 1, 11, 1, 6, 5, 4, 7, 3, 9, 0, 17, 15, 1, 15, 1, 6, 0, 4, 9, 14, 13, 3, 11, 25, 0, 6, 7, 0, 17, 7, 15, 2, 0, 30, 23, 6, 21, 2, 33, 1, 0, 3, 0, 14, 5, 6, 21, 19, 0, 30, 3, 1, 5, 34, 19, 26, 17, 19, 17, 5, 33, 15, 23, 27, 33, 4, 3, 26, 1, 39, 35, 19, 9, 18

Offset

2,4

Comments

Sequence A081504 gives the n such that a(n)=0. For those n, A133831(n) gives the k>n for which the binary trinomial is prime.

Links

T. D. Noe, Table of n, a(n) for n=2..2000

Mathematica

Table[s=1+2^n; k=1; While[k<n && !PrimeQ[s+2^k], k++ ]; If[k==n, 0, k], {n, 100}]

Crossrefs

Cf. A057732, A059242, A057196, A057200, A081091, A095056 (various forms of prime binary trinomials).

Sequence in context: A347062 A321914 A321746 * A316632 A111571 A051509

Adjacent sequences: A133827 A133828 A133829 * A133831 A133832 A133833

Keyword

nonn

Author

T. D. Noe, Sep 26 2007

Status

approved