1,3

This sequence makes its appearance as the first left hand column of 'triangle' A160468.

The first difference with the sequence for the numerators in the Taylor series for tan(x) A002430 occurs at a(12). Its resemblance with this sequence led to the conjecture A160469(n) = A002430(n)*A089170(n-1).

a(n) = A002430(n)*A089170(n-1) with A002430 (n) = numer((-1)^(n-1)*2^(2*n)*(2^(2*n)-1)* bernoulli(2*n)/(2*n)!) and A089170 (n-1) = numer(2*bernoulli(2*n)* (4^n-1)/(2*n))/ numer((4^n-1)*bernoulli(2*n)/(2*n)!) for n = 1, 2, 3, .. .\

Equals the first left hand column of A160468.

Equals A002430(n)*A089170(n-1).

Equals (A002430(n)/A036279(n))*(A117972(n)/A000265(n)).

Equals A048896(n-1)*A002425(n).

Cf. A156769 A 'look-a-like' of the denominators in Taylor series for tan(x).

Sequence in context: A125200 A071402 A002430 this_sequence A037420 A034721 A107815

Adjacent sequences: A160466 A160467 A160468 this_sequence A160470 A160471 A160472

easy,nonn

Johannes W. Meijer (meijgia(AT)hotmail.com), May 24 2009