A119961 Semiprimes that are the sum of two triangular numbers.

4, 6, 9, 10, 15, 21, 22, 25, 34, 38, 39, 46, 49, 51, 55, 57, 58, 65, 69, 87, 91, 93, 94, 106, 111, 115, 119, 121, 123, 133, 141, 142, 146, 159, 169, 177, 183, 202, 205, 213, 214, 218, 219, 226, 235, 237, 249, 253, 254, 259, 262, 265, 267, 274, 289, 291, 295

Offset: 1

Author

Jonathan Vos Post, Aug 02 2006

Keywords

• easy
• nonn

Comments

Semiprime analog of A117048 Prime numbers that are expressible as the sum of two triangular numbers.

Crossrefs

Cf. A001358, A020756, A117048.

Programs

Mathematica

With[{nn=60},Take[Union[Select[Total/@Tuples[Accumulate[Range[0,nn]],2],PrimeOmega[ #] ==2&]],nn]] (* Harvey P. Dale, Nov 04 2020 *)

Formula

A020756 intersection A001358.

Extensions

Missing a(2) and a(19)-a(53) from Giovanni Resta, Jun 13 2016