A224421 The indices of tetrahedral numbers that are also triangular.

0, 1, 3, 8, 20, 34

Offset: 0

Author

Tanya Khovanova, Apr 06 2013

Keywords

• nonn
• full
• fini

Examples

			The eighth tetrahedral number is 120, which is also a triangular number. Hence, 8 belongs to the sequence.
		

Links

• E. T. Avanesov, Solution of a problem on figurate numbers (in Russian), Acta Arith. 12 1966/1967 pages 409-420.

Crossrefs

Cf. A027568, A102349.

Programs

Mathematica

Select[Table[{n,(n(n+1)(n+2))/6},{n,0,35}],OddQ[Sqrt[1+8#[[2]]]]&][[;;,1]] (* Harvey P. Dale, May 31 2024 *)

PARI

for(n=0,34,if(ispolygonal(n*(n+1)*(n+2)/6,3),print1(n", "))) \\ Charles R Greathouse IV, Apr 07 2013