A225787 Least prime number p such that p*triangular(n) is a triangular number, or 0 if no such p exists.

2, 3, 2, 11, 19, 3, 5, 0, 71, 23, 109, 131, 17, 181, 2, 239, 271, 307, 0, 379, 3, 13, 127, 61, 67, 163, 701, 47, 811, 97, 37, 991, 0, 31, 0, 79, 83, 0, 41, 7, 0, 191, 37, 0, 5, 83, 541, 251, 2351, 613, 71, 0, 0, 2861, 743, 3079, 3191, 367, 0, 3539, 229, 0, 977, 0, 4159

Offset: 0

Author

Alex Ratushnyak, May 16 2013

Keywords

• nonn

Examples

			Least prime p such that triangular(3)*p is a triangular number is p=11, so a(3) = 11.
		

Crossrefs

Cf. A000217, A068084, A225502.

Formula

a(n) <= n^2 + n + 2. For n>0, a(n) <= n^n + n + 1.