A079780 a(n) = largest prime <= n*prime(n).

2, 5, 13, 23, 53, 73, 113, 151, 199, 283, 337, 443, 523, 601, 701, 839, 997, 1097, 1259, 1409, 1531, 1733, 1907, 2131, 2423, 2621, 2777, 2971, 3137, 3389, 3931, 4177, 4519, 4723, 5209, 5431, 5807, 6173, 6491, 6917, 7333, 7591, 8209, 8467, 8863, 9151, 9907

Offset

1,1

Comments

a(n) is the largest prime < A079779(n).

Links

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

Formula

a(n) = prime(A057855(n)). - Michel Marcus, Aug 30 2019

Maple

With exception of first term: seq(prevprime(n*ithprime(n)), n=2..40);

Mathematica

PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; Table[ Abs[ PrevPrim[ n*Prime[n]]], {n, 1, 50}]
Table[Abs[NextPrime[n Prime[n], -1]], {n, 50}] (* Harvey P. Dale, May 25 2012 *)

Prog

(PARI) for(n=1, 47, print1(precprime(n*prime(n)), ", "))

Crossrefs

Cf. A057855, A079779.

Sequence in context: A256491 A106009 A194552 * A178621 A362105 A309230

Adjacent sequences: A079777 A079778 A079779 * A079781 A079782 A079783

Keyword

nonn

Author

Amarnath Murthy, Feb 03 2003

Extensions

Edited and extended by Robert G. Wilson v, Klaus Brockhaus and Mark Hudson (mrmarkhudson(AT)hotmail.com), Feb 04 2003

Status

approved