A123359 Least m such that 3^n+2^m is prime.

0, 1, 1, 1, 1, 3, 2, 4, 1, 2, 1, 6, 4, 3, 1, 1, 11, 6, 7, 21, 3, 8, 2, 5, 1, 7, 1, 4, 12, 11, 2, 4, 7, 10, 15, 6, 1, 30, 3, 8, 11, 11, 2, 6, 3, 16, 14, 17, 17, 4, 18, 50, 36, 6, 71, 6, 29, 2, 11, 6, 4, 16, 18, 1, 8, 6, 17, 9, 15, 14, 54, 12, 17, 12, 41, 4, 29, 3, 7, 25, 11, 35, 23, 24, 31, 27, 18

Offset

0,6

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

Example

a(0)=0 because 3^0+2^0=1+1=2 is prime,
a(5)=3 because 3^5+2^3=243+8=251 is prime.

Mathematica

lm[n_]:=Module[{c=3^n, m=0}, While[!PrimeQ[c+2^m], m++]; m]; Array[lm, 90, 0] (* Harvey P. Dale, May 01 2013 *)

Crossrefs

Cf. A123340 = least m such that 2^n+3^m is prime, A123342 = least m such that 2^n+5^m is prime.

Sequence in context: A097673 A226377 A140430 * A121885 A187760 A122143

Adjacent sequences: A123356 A123357 A123358 * A123360 A123361 A123362

Keyword

nonn

Author

Zak Seidov, Oct 12 2006

Status

approved