A161550 Largest prime <= n^2+n.

2, 5, 11, 19, 29, 41, 53, 71, 89, 109, 131, 151, 181, 199, 239, 271, 293, 337, 379, 419, 461, 503, 547, 599, 647, 701, 751, 811, 863, 929, 991, 1051, 1117, 1187, 1259, 1327, 1399, 1481, 1559, 1637, 1721, 1801, 1889, 1979, 2069, 2161, 2251, 2351, 2447, 2549, 2647

Offset: 1

Author

Daniel Tisdale, Jun 13 2009

Keywords

• easy
• nonn

Links

• Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Programs

Maple

A161550 := proc(n) return prevprime(n*(n+1)+1): end: seq(A161550(n),n=1..51); # Nathaniel Johnston, May 01 2011

Mathematica

PrimePrev[n_]:=Module[{k},k=n-1;While[ !PrimeQ[k],k-- ];k]; lst={};Do[a=n^2+n;p=PrimePrev[a];AppendTo[lst,p],{n,2,5!}];lst (* Vladimir Joseph Stephan Orlovsky, Jun 13 2009 *)
Join[{2},Table[NextPrime[n^2+n,-1],{n,2,60}]] (* Harvey P. Dale, May 01 2011 *)

PARI

a(n)=precprime(n^2+n) \\ Charles R Greathouse IV, Mar 27 2014

Extensions

More terms from Vladimir Joseph Stephan Orlovsky, Jun 13 2009