A379609 Triples (x,y,z) such that T(x)*T(y) = T(z) with 2 <= x <= y, where T(n) is the n-th triangular number, sorted first by values of z, then by values of x.

3, 3, 8, 2, 5, 9, 4, 6, 20, 2, 20, 35, 3, 14, 35, 4, 12, 39, 5, 11, 44, 7, 10, 55, 5, 19, 75, 3, 34, 84, 9, 13, 90, 6, 21, 98, 2, 76, 132, 6, 33, 153, 4, 55, 175, 14, 18, 189, 13, 20, 195, 12, 23, 207, 15, 20, 224, 14, 22, 230, 11, 28, 231, 12, 29, 260, 7, 51, 272, 10, 38, 285, 11, 36, 296, 5, 90, 350, 3, 143, 351, 10, 50, 374, 7, 75, 399, 9, 68, 459, 19, 34, 475

Offset

1,1

Links

Table of n, a(n) for n=1..93.

Example

Triples begin:
  3,  3,  8;
  2,  5,  9;
  4,  6, 20;
  2, 20, 35;
  3, 14, 35;
  4, 12, 39;
  5, 11, 44;
  7, 10, 55;
  ...
The triple 2,5,9 is in this sequence because the second triangular number (3) times the fifth (15) is the ninth (45).

Crossrefs

Cf. A000217, A188630, A198453 (additive), A225390.

Sequence in context: A212636 A282255 A164040 * A154178 A276800 A332684

Adjacent sequences: A379606 A379607 A379608 * A379610 A379611 A379612

Keyword

nonn,tabf

Author

Kelvin Voskuijl, Dec 27 2024

Status

approved