A013605 a(n) = 5^n-prevprime(5^n).

2, 2, 12, 6, 4, 6, 4, 44, 16, 6, 12, 12, 52, 2, 4, 62, 16, 102, 16, 26, 54, 54, 36, 38, 64, 2, 12, 42, 16, 102, 18, 72, 42, 68, 256, 18, 52, 84, 234, 54, 34, 72, 274, 266, 36, 14, 4, 56, 162, 2, 24, 122, 6, 14, 94, 446, 72, 56, 298, 384, 28, 26

Offset: 1

Author

James Kilfiger (mapdn(AT)csv.warwick.ac.uk)

Keywords

• nonn

Links

• Daniel Starodubtsev, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000351, A104090.

Programs

Maple

seq(5^i-prevprime(5^i),i=1..100);

Mathematica

#-NextPrime[#,-1]&/@(5^Range[70])  (* Harvey P. Dale, Mar 12 2011 *)

PARI

a(n) = 5^n - precprime(5^n-1); \\ Michel Marcus, Aug 14 2019