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

0,2

Comments

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

Links

Table of n, a(n) for n=0..13.

Formula

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

Crossrefs

Cf. A125053, A125054.

Sequence in context: A249961 A177074 A069405 * A160397 A303653 A185809

Adjacent sequences: A125052 A125053 A125054 * A125056 A125057 A125058

Keyword

nonn

Author

Paul D. Hanna, Nov 21 2006

Status

approved