A227276 Primes p for which p^2 + p - 1 = q*r (q

7, 17, 23, 61, 67, 71, 79, 151, 307, 311, 383, 389, 409, 439, 613, 677, 1559, 1627, 1637, 2377, 2719, 2801, 3407, 3821, 4229, 4799, 4919, 5557, 5641, 5743, 5779, 5851, 5867, 6133, 6733, 7121, 7723, 8009, 8527, 8573, 10163, 10729, 11317, 11789, 11987, 14107, 14629, 14653, 14669, 17189, 17401, 18077

Offset: 1

Author

Vladimir Shevelev, Jul 04 2013

Keywords

• nonn

Links

• Peter J. C. Moses, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A227129, A226770.

Programs

Mathematica

Select[Prime[Range[3000]],And@@PrimeQ[#1^2-1+First[#2]]&&Last[#2]=={1,1}&[#1,Transpose[FactorInteger[#^2+#-1]]]&] (* Peter J. C. Moses, Jul 05 2013 *)

Formula

A226770(a^2(n) - 1) = 3.

Extensions

More terms from Peter J. C. Moses.