A226070 Numbers n such that n^2-1 is a triangular number and n^2+1 is a prime.

1, 2, 4, 134, 2174, 154634

Offset

1,2

Comments

Subsequence of A006452 that consists of the terms n such that n^2+1 is prime.

a(7) is too large to include here (see b-file). - Max Alekseyev, Jan 30 2014

Links

Max Alekseyev, Table of n, a(n) for n = 1..12

Mathematica

Select[Range[155000], PrimeQ[#^2+1]&&OddQ[Sqrt[8(#^2-1)+1]]&] (* Harvey P. Dale, Jul 19 2019 *)

Prog

(C) // see A226069.

Crossrefs

Corresponding primes: A226069.

Indices of corresponding triangular numbers: A226071.

Cf. A226072-A226074.

Sequence in context: A018500 A353790 A271677 * A013552 A018512 A018517

Adjacent sequences: A226067 A226068 A226069 * A226071 A226072 A226073

Keyword

nonn

Author

Alex Ratushnyak, May 25 2013

Extensions

Terms a(7)-a(12) from Max Alekseyev, Jan 30 2014

Status

approved