A013606 a(n) = 4^n - prevprime(4^n).

1, 3, 3, 5, 3, 3, 3, 15, 5, 3, 3, 3, 5, 57, 35, 5, 41, 5, 45, 87, 11, 17, 21, 59, 27, 47, 33, 5, 27, 93, 57, 59, 5, 23, 35, 93, 35, 15, 11, 65, 57, 35, 35, 299, 33, 83, 3, 17, 51, 15, 33, 17, 117, 59, 21, 75, 11, 3, 5, 119, 3, 59, 137, 159, 5, 347, 45, 113, 105, 27, 111

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. A000302, A104089.

Programs

Maple

seq(4^i-prevprime(4^i),i=1..100);

Mathematica

#-NextPrime[#,-1]&/@(4^Range[80]) (* Harvey P. Dale, Dec 13 2016 *)

PARI

a(n) = 4^n - precprime(4^n); \\ Michel Marcus, Sep 01 2019

Formula

a(n) = A000302(n) - A104089(n). - Michel Marcus, Sep 01 2019