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A296792 Expansion of e.g.f. (sec(x) + tan(x))/sqrt(1 - 2*x). 3
1, 2, 6, 29, 196, 1721, 18622, 239427, 3563880, 60247537, 1139848346, 23857033243, 547234058732, 13650416199369, 367871731383990, 10651249531927427, 329733427896399952, 10868107639700229857, 379980639501713082034, 14046060369812427842859, 547335961798415004947220 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Boustrophedon transform of A001147.

LINKS

Robert Israel, Table of n, a(n) for n = 0..403

J. Millar, N. J. A. Sloane and N. E. Young, A new operation on sequences: the Boustrophedon transform, J. Combin. Theory, 17A (1996), 44-54 (Abstract, pdf, ps)

N. J. A. Sloane, Transforms

Index entries for sequences related to boustrophedon transform

Index entries for sequences related to factorial numbers

FORMULA

a(n) ~ (sec(1/2) + tan(1/2)) * 2^(n + 1/2) * n^n / exp(n). - Vaclav Kotesovec, Dec 21 2017

MAPLE

S:= series((sec(x)+tan(x))/sqrt(1-2*x), x, 51):

seq(coeff(S, x, n)*n!, n=0..50); # Robert Israel, Dec 21 2017

MATHEMATICA

nmax = 20; CoefficientList[Series[(Sec[x] + Tan[x])/Sqrt[1 - 2 x], {x, 0, nmax}], x] Range[0, nmax]!

PROG

(PARI) first(n) = x='x+O('x^n); Vec(serlaplace((1/cos(x) + tan(x))/sqrt(1-2*x))) \\ Iain Fox, Dec 21 2017

CROSSREFS

Cf. A000111, A000754, A001147, A230960, A230961.

Sequence in context: A124529 A246385 A260578 * A241462 A187006 A321961

Adjacent sequences:  A296789 A296790 A296791 * A296793 A296794 A296795

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, Dec 20 2017

STATUS

approved

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Last modified September 26 20:34 EDT 2021. Contains 347672 sequences. (Running on oeis4.)