A226071 Numbers k such that triangular(k)+1 is a square and triangular(k)+2 is a prime.

0, 2, 5, 189, 3074, 218685

Offset: 1

Author

Alex Ratushnyak, May 25 2013

Keywords

• nonn
• changed

Comments

Subsequence of A006451 that contains the terms k such that triangular(k)+2 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

Crossrefs

Corresponding primes: A226069.

Roots of corresponding squares: A226070.

Cf. A226071-A226074.

Programs

C

// see A226069.

Mathematica

Select[Range[0,220000],IntegerQ[Sqrt[(#(#+1))/2+1]]&&PrimeQ[(#(#+1))/2+2]&] (* Harvey P. Dale, Mar 01 2023 *)

Extensions

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