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

1,1

Comments

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

Links

Table of n, a(n) for n=1..57.

Formula

A020756 intersection A001358.

Mathematica

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

Crossrefs

Cf. A001358, A020756, A117048.

Sequence in context: A084662 A137167 A181564 * A122492 A178378 A133234

Adjacent sequences: A119958 A119959 A119960 * A119962 A119963 A119964

Keyword

easy,nonn

Author

Jonathan Vos Post, Aug 02 2006

Extensions

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

Status

approved