A124887 Least positive k such that n * 2^n + k is prime.

1, 3, 5, 3, 3, 5, 11, 5, 13, 3, 3, 5, 5, 17, 7, 7, 19, 25, 15, 9, 61, 49, 7, 5, 17, 5, 13, 3, 9, 29, 33, 9, 73, 13, 39, 5, 53, 39, 7, 3, 7, 5, 45, 5, 19, 19, 73, 31, 141, 83, 29, 49, 25, 11, 21, 53, 37, 49, 39, 13, 41, 9, 47, 25, 61, 139, 33, 11, 133, 39, 93, 49, 93, 41, 7, 15, 67, 121

Offset

1,2

References

J. Earls, Red Zen, Lulu Press, NY, 2006, p. 135.

Links

Table of n, a(n) for n=1..78.

Mathematica

lpk[n_]:=Module[{c=n*2^n, k=1}, While[!PrimeQ[c+k], k=k+2]; k]; Array[lpk, 80] (* Harvey P. Dale, Oct 08 2017 *)

Crossrefs

Sequence in context: A102294 A358790 A021287 * A304903 A097524 A073703

Adjacent sequences: A124884 A124885 A124886 * A124888 A124889 A124890

Keyword

easy,nonn

Author

Jason Earls, May 19 2007

Status

approved