A125055 Diagonal of symmetric triangle A125053 located immediately below the central terms (A125054).

1, 15, 285, 8475, 378105, 23823015, 2018820885, 221605991475, 30596648805105, 5189967817758015, 1061021392126671885, 257296819626005894475, 73023341368629447792105, 23978466652359211809453015

Offset: 0

Author

Paul D. Hanna, Nov 21 2006

Keywords

• nonn

Comments

Triangle A125053 is a variant of triangle A008301 (enumeration of binary trees) such that the leftmost column gives the secant numbers (A000364).

Crossrefs

Cf. A125053, A125054.

Formula

a(n) = A125054(n+1) - 2*A125054(n). - Philippe Deléham, Jul 22 2007