A118749 Largest prime <= 3*n.

3, 5, 7, 11, 13, 17, 19, 23, 23, 29, 31, 31, 37, 41, 43, 47, 47, 53, 53, 59, 61, 61, 67, 71, 73, 73, 79, 83, 83, 89, 89, 89, 97, 101, 103, 107, 109, 113, 113, 113, 113, 113, 127, 131, 131, 137, 139, 139, 139, 149, 151, 151, 157, 157, 163, 167, 167, 173, 173, 179, 181

Offset

1,1

Comments

Analogous to A060308 largest prime <= 2*k.

Links

Table of n, a(n) for n=1..61.

Formula

a(n) = A007917(A008585(n)). - Michel Marcus, Nov 25 2015

Mathematica

Table[Max[FactorInteger[(3 n)!/(n!)^3]], {n, 1, 70}] (* Vincenzo Librandi, Nov 25 2015 *)
NextPrime[3*Range[70]+1, -1] (* Harvey P. Dale, Nov 12 2017 *)

Prog

(Magma) [NthPrime(#PrimesUpTo(3*n)): n in [1..100]]; // Vincenzo Librandi, Nov 25 2015
(PARI) vector(100, n, precprime(3*n)) \\ Altug Alkan, Nov 25 2015

Crossrefs

Cf. A007917 (largest prime <= n), A008585 (3n).

Cf. A060308, A118750, A118751, A118752.

Essentially the same as A081259.

Sequence in context: A255602 A319181 A318718 * A367227 A355821 A332075

Adjacent sequences: A118746 A118747 A118748 * A118750 A118751 A118752

Keyword

easy,nonn

Author

Jonathan Vos Post, Apr 29 2006

Status

approved