A125055 - OEIS

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

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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