A226856 Numbers A226770((prime(n))^2-1).

1, 1, 1, 3, 1, 1, 3, 1, 3, 5, 1, 46, 1, 5, 66, 1, 1, 3, 3, 3, 10, 3, 1, 1, 172, 1, 1, 398, 5, 132, 255, 1, 336, 41, 1, 3, 615, 1, 462, 918, 283, 1, 1, 1, 453, 1, 11, 713, 1503, 311, 1, 112, 1, 308, 2272, 1, 788, 481, 2301, 1, 2686, 1358, 3, 3, 2651, 3346, 1

Offset: 1

Author

Vladimir Shevelev, Jun 19 2013

Keywords

• nonn

Comments

a(n) = 1 iff (prime(n))^2 + prime(n) - 1 is prime (A053184).

Links

• Peter J. C. Moses, Table of n, a(n) for n = 1..400

Crossrefs

Cf. A226770, A053184.

Programs

Mathematica

Table[(div=Most[Divisors[n+1]]; Length[FixedPoint[Union[Flatten[AppendTo[div, Map[Most[Rest[Divisors[n+#]]]&, #]]]]&, div]]-1), {n, Prime[Range[40]]^2-1}] (* Peter J. C. Moses, Jun 20 2013 *)

Extensions

More terms from Peter J. C. Moses, Jun 20 2013