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 A354335 a(n) is the denominator of Sum_{k=0..n} 1 / (2*k)!. 5
 1, 2, 24, 720, 4480, 518400, 479001600, 29059430400, 20922789888000, 6402373705728000, 810967336058880000, 1124000727777607680000, 88635485961891348480000, 14936720782466875392000000, 27717122237428532772864000000, 265252859812191058636308480000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Table of n, a(n) for n=0..15. FORMULA Denominators of coefficients in expansion of cosh(sqrt(x)) / (1 - x). EXAMPLE 1, 3/2, 37/24, 1111/720, 6913/4480, 799933/518400, 739138093/479001600, ... MATHEMATICA 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 PROG (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 CROSSREFS Cf. A010050, A053556, A061355, A073743, A143383, A354331, A354333, A354334 (numerators). Sequence in context: A009750 A030438 A012723 * A069150 A323491 A046977 Adjacent sequences: A354332 A354333 A354334 * A354336 A354337 A354338 KEYWORD nonn,frac AUTHOR Ilya Gutkovskiy, May 24 2022 STATUS approved

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Last modified December 9 07:37 EST 2023. Contains 367689 sequences. (Running on oeis4.)