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
Offset: 0
Links
- Peter Luschny, The lost Bernoulli numbers.
Programs
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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);
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Mathematica
ez[n_] := SeriesCoefficient[Sec[t] + Tan[t], {t, 0, n}]; a[0] = 1; a[n_] := Denominator[ez[n - 1] n!/(4^n - 2^n)]; Table[a[n], {n, 0, 28}] (* Jean-François Alcover, Jun 26 2019 *)