A123342 -id:A123342 - cp's OEIS frontend

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

Zak Seidov, Oct 12 2006

nonn

			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.

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

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

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 *)

A123360 Least m such that 5^n+2^m is prime.

Original entry on oeis.org

0, 1, 2, 1, 4, 7, 2, 5, 12, 5, 2, 15, 8, 5, 10, 37, 24, 1, 14, 17, 28, 41, 16, 145, 44, 101, 8, 35, 64, 43, 74, 63, 24, 35, 16, 13, 88, 81, 14, 53, 44, 21, 46, 89, 56, 7, 70, 97, 200, 59, 8, 35, 24, 45, 22, 53, 12, 77, 6, 19, 4, 165, 18, 5, 488, 157, 26, 101, 120, 59, 4, 115, 44, 89

Offset: 0

Zak Seidov, Oct 12 2006

nonn

			a(0)=0 because 5^0+2^0=1+1=2 is prime,
a(5)=7 because 5^5+2^7=3125+128=3253 is prime,

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

Cf. A123340, A123342.

lm[n_]:=Module[{c=5^n,m=1},While[CompositeQ[c+2^m],m++];m]; Join[ {0},Array[lm,80]] (* Harvey P. Dale, Jul 18 2021 *)

cp's OEIS Frontend

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

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