A065384 Largest prime <= n * (n + 1) / 2.

3, 5, 7, 13, 19, 23, 31, 43, 53, 61, 73, 89, 103, 113, 131, 151, 167, 181, 199, 229, 251, 271, 293, 317, 349, 373, 401, 433, 463, 491, 523, 557, 593, 619, 661, 701, 739, 773, 811, 859, 887, 941, 983, 1033, 1069, 1123, 1171, 1223, 1259, 1321, 1373, 1429, 1483

Offset: 2

Author

Reinhard Zumkeller, Nov 05 2001

Keywords

• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 2..1000

Crossrefs

Cf. A065382, A053001, A064383, A000217.

Programs

Mathematica

PrimePrev[n_]:=Module[{k=n},While[ !PrimeQ[k],k-- ];k];f[n_]:=n*(n+1)/2;lst={};Do[AppendTo[lst,PrimePrev[f[n]]],{n,6!}];lst (* Vladimir Joseph Stephan Orlovsky, Feb 26 2010 *)

PARI

{ for (n=2, 1000, write("b065384.txt", n, " ", precprime(n*(n + 1)/2)) ) } [Harry J. Smith, Oct 17 2009]