A158526 n and (1 + 2*n + 2*n^2) are primes.

2, 5, 7, 17, 19, 29, 47, 79, 97, 109, 137, 139, 149, 157, 167, 199, 229, 347, 349, 389, 409, 467, 479, 547, 577, 599, 709, 719, 757, 857, 929, 937, 967, 1039, 1069, 1087, 1187, 1229, 1259, 1399, 1409, 1447, 1559, 1579, 1597, 1607, 1657, 1697, 1699, 1709

Offset: 1

Author

Zak Seidov, Mar 20 2009

Keywords

• nonn
• easy

Comments

Numbers n such that A048395(n) is semiprime, or A048395(n)/n is prime.

Or, primes in A027861. Also, (1+2*n+2*n^2) are in A027862. - Zak Seidov, Sep 19 2015

Examples

			A048395(2)=26=2*13, A048395(5)=305=5*61, A048395(7)=791=7*113.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A048395 (sum of consecutive nonsquares), A001358 (semiprimes).

Cf. A027861, A027862.

Programs

Magma

[p: p in PrimesUpTo(2000) | IsPrime(2*p^2+2*p+1)]; // Vincenzo Librandi, Jun 22 2014

Mathematica

f[n_]:=PrimeQ[n^2+(n+1)^2];lst={};Do[p=Prime[n];If[f[p],AppendTo[lst,p]],{n,6!}];lst (* Vladimir Joseph Stephan Orlovsky, Oct 27 2009 *)

PARI

forprime(p=2,1e4,if(isprime(2*p*(p+1)+1),print1(p","))) \\ Charles R Greathouse IV, Sep 09 2009