A193473 - OEIS

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A193473

Denominator of ez(n-1)*n!/(4^n-2^n) where ez(n) is the n-th coefficient of sec(t)+tan(t) for n>0, a(0) = 1.

1, 2, 6, 56, 30, 992, 42, 16256, 30, 261632, 66, 4192256, 2730, 67100672, 6, 1073709056, 510, 17179738112, 798, 274877382656, 330, 628292059136, 138, 70368735789056, 2730, 1125899873288192, 6, 18014398375264256, 870

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..28.

Peter Luschny, The lost Bernoulli numbers.

MAPLE

gf := (f, n) -> coeff(series(f(x), x, n+1), x, n):

BG := n ->`if`(n=0, 1, gf(sec+tan, n-1)*n!/(4^n-2^n)):

A193473 := n -> denom(BG(n)): seq(A193473(n), n=0..28);

MATHEMATICA

ez[n_] := SeriesCoefficient[Sec[t] + Tan[t], {t, 0, n}];