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A354335
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a(n) is the denominator of Sum_{k=0..n} 1 / (2*k)!.
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5
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1, 2, 24, 720, 4480, 518400, 479001600, 29059430400, 20922789888000, 6402373705728000, 810967336058880000, 1124000727777607680000, 88635485961891348480000, 14936720782466875392000000, 27717122237428532772864000000, 265252859812191058636308480000000
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OFFSET
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0,2
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LINKS
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FORMULA
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Denominators of coefficients in expansion of cosh(sqrt(x)) / (1 - x).
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EXAMPLE
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1, 3/2, 37/24, 1111/720, 6913/4480, 799933/518400, 739138093/479001600, ...
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MATHEMATICA
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Table[Sum[1/(2 k)!, {k, 0, n}], {n, 0, 15}] // Denominator
nmax = 15; CoefficientList[Series[Cosh[Sqrt[x]]/(1 - x), {x, 0, nmax}], x] // Denominator
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PROG
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(PARI) a(n) = denominator(sum(k=0, n, 1/(2*k)!)); \\ Michel Marcus, May 24 2022
(Python)
from fractions import Fraction
from math import factorial
def A354335(n): return sum(Fraction(1, factorial(2*k)) for k in range(n+1)).denominator # Chai Wah Wu, May 24 2022
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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