A326917 Nonnegative numbers of the form 8*T(x) - T(y) with 0 <= x, 0 <= y, where T() denotes a triangular number.

0, 2, 3, 5, 7, 8, 9, 12, 14, 15, 18, 20, 21, 23, 24, 25, 27, 29, 32, 33, 34, 35, 38, 42, 44, 45, 47, 48, 52, 53, 54, 57, 59, 60, 62, 63, 65, 70, 71, 74, 75, 77, 78, 79, 80, 84, 88, 89, 90, 92, 93, 96, 98, 99, 102, 104, 105, 107, 110, 113, 114, 115, 117, 119

Offset: 1

Author

Ralf Steiner, Oct 21 2019

Keywords

• nonn

Comments

When incremented by 1 this is also the difference between an odd square (1 + 8*T) and a triangular number T.

Examples

			8*A000217(1) - A000217(2) = 8*1 - 3 = 5 = a(4).
		

Crossrefs

Cf. A000217 (T), A175035, A016754 (odd squares).

Programs

Mathematica

T[n_] := n (n + 1)/2;Select[Union[Flatten[Table[8 T[x] - T[y], {x, 0, 15}, {y, 0, 100}]]],115 >= # >= 0 &]

Formula

a(n) = A175035(n) - 1.