login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A193476 The denominators of the Bernoulli secant numbers at odd indices. 1
2, 56, 992, 16256, 261632, 4192256, 67100672, 1073709056, 17179738112, 274877382656, 628292059136, 70368735789056, 1125899873288192, 18014398375264256, 288230375614840832, 4611686016279904256, 73786976286248271872, 1180591620683051565056 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Denominator of the coefficient [x^(2n)] of sec(x)*(2*n+1)!/(4*16^n-2*4^n), that is, a(n) is the denominator of A000364(n)*(2*n+1)/(4*16^n-2*4^n). [Edited by Altug Alkan, Apr 22 2018]

Numerators are A009843.

A193475(n) = 4*16^n-2*4^n is similar, but differs at n = 10, 31, 52, 73, 77, 94, ...

LINKS

Table of n, a(n) for n=0..17.

Peter Luschny, The lost Bernoulli numbers.

MAPLE

gf := (f, n) -> coeff(series(f(x), x, n+4), x, n):

A193476 := n -> denom(gf(sec+tan, 2*n)*(2*n+1)!/(4*16^n - 2*4^n)):

seq(A193476(n), n = 0..17);

gf := (f, n) -> coeff(series(f(x), x, n+4), x, n):

A193476 := n -> denom(gf(sec, 2*n)*(2*n+1)!/(4*16^n - 2*4^n)):

seq(A193476(n), n = 0..17); # Altug Alkan, Apr 23 2018

PROG

a(n) = denominator(subst(bernpol(2*n+1), 'x, 1/4)*2^(2*n+1)/(2^(2*n+1)-1)); \\ Altug Alkan, Apr 22 2018 after Charles R Greathouse IV at A000364

CROSSREFS

Cf. A000364, A009843, A160144, A193475.

Sequence in context: A080313 A080268 A224297 * A193475 A246001 A009555

Adjacent sequences:  A193473 A193474 A193475 * A193477 A193478 A193479

KEYWORD

nonn,frac

AUTHOR

Peter Luschny, Aug 17 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified June 21 16:12 EDT 2018. Contains 305624 sequences. (Running on oeis4.)