A031215 Even-indexed primes: a(n) = prime(2n).

3, 7, 13, 19, 29, 37, 43, 53, 61, 71, 79, 89, 101, 107, 113, 131, 139, 151, 163, 173, 181, 193, 199, 223, 229, 239, 251, 263, 271, 281, 293, 311, 317, 337, 349, 359, 373, 383, 397, 409, 421, 433, 443, 457, 463, 479, 491, 503, 521, 541, 557, 569

Offset: 1

Author

Jeff Burch

Keywords

• nonn
• easy

Comments

Also every second odd prime. - Cino Hilliard, Dec 02 2007

If n > 1, then a(n) is less than, and asymptotic to, the n-th Ramanujan prime R_n = A104272(n). Research questions on the difference R_n - a(n) are at A104272. - Jonathan Sondow, Dec 16 2013

Links

• Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A031368 (odd-indexed primes), A104272, A105720, A161463, A179740, A233739.

Programs

Magma

[ NthPrime(2*n): n in [1..1000] ]; // Vincenzo Librandi, Apr 11 2011

Maple

A031215 := n->ithprime(2*n);

Mathematica

Table[ Prime[ 2n], {n, 52}] (* Robert G. Wilson v, Dec 01 2013 *)

PARI

a(n)=prime(2*n) \\ Charles R Greathouse IV, Jul 02 2013

Formula

a(n) = A104272(n) - A233739(n). - Jonathan Sondow, Dec 16 2013

a(n) = A105720(n) - A161463(n). - Torlach Rush, May 31 2021