A013607 a(n) = 6^n-prevprime(6^n).

1, 5, 5, 5, 17, 7, 17, 7, 7, 7, 59, 19, 17, 13, 7, 19, 49, 13, 19, 7, 23, 35, 19, 89, 17, 119, 29, 55, 5, 19, 5, 59, 85, 5, 17, 35, 59, 83, 49, 115, 19, 23, 43, 109, 103, 7, 23, 19, 7, 245, 43, 13, 5, 55, 89, 83, 143, 53, 53, 383, 7, 55, 113, 37, 5, 23, 143, 115

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. A000400 (6^n), A104091 (largest prime <= 6^n).

Programs

Maple

seq(6^i-prevprime(6^i),i=1..100);

Mathematica

pp[n_]:=Module[{n6=6^n},n6-NextPrime[n6,-1]]; Array[pp,70] (* Harvey P. Dale, May 04 2011 *)
#-NextPrime[#,-1]&/@(6^Range[70]) (* Harvey P. Dale, May 28 2023 *)

Formula

a(n) = A000400(n) - A104091(n). - Michel Marcus, Jan 13 2020