A100021 a(n) = 3*prime(n) - prime(n+1) - 3.

0, 1, 5, 7, 17, 19, 29, 31, 37, 53, 53, 67, 77, 79, 85, 97, 113, 113, 127, 137, 137, 151, 157, 167, 187, 197, 199, 209, 211, 209, 247, 253, 269, 265, 293, 293, 305, 319, 325, 337, 353, 349, 377, 379, 389, 383, 407, 439, 449, 451, 457, 473, 469, 493, 505, 517, 533, 533, 547

Offset: 1

Author

Giovanni Teofilatto, Nov 20 2004

Keywords

• nonn
• less

Comments

Except for the initial term, a(n)==(1,5) mod 6.

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A099389 for the primes arising in the sequence, A098764.

Programs

Maple

f:=n->3*ithprime(n)-ithprime(n+1)-3;

Mathematica

3#[[1]]-#[[2]]-3&/@Partition[Prime[Range[80]],2,1] (* Harvey P. Dale, Oct 13 2018 *)

PARI

a(n) = 3*prime(n) - prime(n+1) - 3; \\ Michel Marcus, Jan 31 2023

Formula

a(n) = A098764(n) - 3.

Extensions

Corrected by Neven Juric (neven.juric(AT)apis-it.hr), rechecked by N. J. A. Sloane, Jun 13 2006