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A119961
Semiprimes that are the sum of two triangular numbers.
0
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.
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
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