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A089170 Numerator of 2*BernoulliB[2*(n+1)]*(4^(n+1)-1)/(2*(n+1))] divided by numerator of the series coefficients of 1/(1 + Cosh[x]). 5
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 17, 1, 1, 1, 1, 1, 1, 1, 527, 1, 1, 1, 1, 31, 1, 1, 731, 1, 41, 1, 1, 1, 37, 1333, 17, 1, 1, 1, 31, 1, 1, 1, 17, 73, 1, 1, 1, 43, 1271, 59, 629, 1, 73, 2759, 43, 1, 1, 1, 17, 1, 67, 7519, 1, 31, 89, 1, 289, 1, 29020032511, 1, 10573, 1, 1, 1, 2227, 486029 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,12

COMMENTS

Ratios of two similar sequences.

This sequence is related to the sequences of the numerators and denominators in Taylor series for tan(x), i.e., A002430 and A036279, and their "look-alikes", i.e., A160469 and A156769. - Johannes W. Meijer, May 24 2009

LINKS

Michael De Vlieger, Table of n, a(n) for n = 0..5000

FORMULA

For n>=0, a(n)=c(n+1) where c(n)=numerator((4^n-1)*B(2*n)/n)/numerator((4^n-1)*B(2*n)/(2*n)!), B(k) denotes the k-th Bernoulli number. - C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 19 2004

MAPLE

seq(numer(2*bernoulli(2*n)*(4^n-1)/(2*n))/numer((4^n-1)*bernoulli(2*n)/(2*n)!), n=1..100); # C. Ronaldo

MATHEMATICA

Table[Numerator[2*BernoulliB[2*n]*(4^n -1)/(2*n)]/Numerator[SeriesCoefficient[Series[1/(1+Cosh[x]), {x, 0, 2n}], 2n-2]], {n, 1, 128}]

CROSSREFS

Cf. A002425.

From Johannes W. Meijer, May 24 2009: (Start)

Equals A160469(n+1)/A002430(n+1).

Equals A156769(n+1)/A036279(n+1).

(End)

Sequence in context: A241027 A176728 A088469 * A040292 A040293 A040294

Adjacent sequences:  A089167 A089168 A089169 * A089171 A089172 A089173

KEYWORD

nonn

AUTHOR

Wouter Meeussen, Dec 07 2003

STATUS

approved

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Last modified February 20 06:45 EST 2018. Contains 299358 sequences. (Running on oeis4.)