A112355 Triangular numbers that are the sum of three positive triangular numbers.

3, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, 300, 325, 351, 378, 406, 435, 465, 496, 528, 561, 595, 630, 666, 703, 741, 780, 820, 861, 903, 946, 990, 1035, 1081, 1128, 1176, 1225, 1275, 1326

Offset: 1

Author

Rick L. Shepherd, Sep 06 2005

Keywords

• nonn

Comments

A112353 is a subsequence: it requires the three positive triangular numbers to be distinct. The positive terms of A076140 are a subsequence.

Examples

			21 is a term because 21 = 3 + 3 + 15 and these four numbers are positive triangular numbers (A000217(6) = A000217(2) + A000217(2) + A000217(5)). {Also 21 = 1 + 10 + 10 = A000217(1) + A000217(4) + A000217(4).}.
		

Crossrefs

Cf. A000217 (triangular numbers), A089982 (triangular numbers that are the sum of two positive triangular numbers), A112353, A076140 (the three triangular numbers summed are identical).