

A000318


Generalized tangent numbers d(4,n).
(Formerly M3713 N1517)


6



4, 128, 16384, 4456448, 2080374784, 1483911200768, 1501108249821184, 2044143848640217088, 3605459138582973251584, 7995891855149741436305408, 21776918737280678860353961984, 71454103701490016776039304265728, 278008871543597996197497752082448384
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OFFSET

1,1


REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

T. D. Noe, Table of n, a(n) for n = 1..100
D. Shanks, Generalized Euler and class numbers. Math. Comp. 21 (1967) 689694.
D. Shanks, Corrigenda to: "Generalized Euler and class numbers", Math. Comp. 22 (1968), 699
D. Shanks, Generalized Euler and class numbers, Math. Comp. 21 (1967), 689694; 22 (1968), 699. [Annotated scanned copy]
Eric Weisstein's World of Mathematics, Padé approximants.


FORMULA

a(n) = 2^(4n2) * A000182(n).
The g.f. has the following continued fraction expansion: g.f. = [4, b(0), c(0), b(1), c(1), b(2), c(2), ...] where b(n) = (Sum_{k=0..n} 1/(2*k+1))^2 / (128*(n+1)*x), c(n) = 4/((2*n+3)*(Sum_{k=0..n} 1/(2*k+1))*(Sum_{k=0..n+1} 1/(2*k+1))) and each convergent of this continued fraction is a Padé approximant of the Maclaurin series Sum_{k>=1} a(n)*x^(n1).  Thomas Baruchel, Oct 19 2005
a(n) = (2*n1)!*[x^(2*n1)](sec(4*x)*sin(4*x)).  Peter Luschny, Nov 21 2021


MAPLE

egf := sec(4*x)*sin(4*x): ser := series(egf, x, 26):
seq((2*n1)!*coeff(ser, x, 2*n1), n = 1..12); # Peter Luschny, Nov 21 2021


MATHEMATICA

nn = 30; t = Rest@Union[Range[0, nn  1]! CoefficientList[Series[Tan[x], {x, 0, nn}], x]]; t2 = t*2^Range[2, 2*nn, 4] (* T. D. Noe, Jun 19 2012 *)


CROSSREFS

Cf. A000182, A000191, A000490, A349264.
Sequence in context: A013823 A321233 A130318 * A229385 A141367 A141368
Adjacent sequences: A000315 A000316 A000317 * A000319 A000320 A000321


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), Jun 03 2000


STATUS

approved



