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A370379
Number of compositions of n where there are (2*k)!/2 sorts of part k.
1
1, 1, 13, 385, 21061, 1864921, 243833533, 44133789745, 10556951897461, 3223557261840841, 1223184443268467053, 564530822421956927905, 311384269987431969105061, 202282520358685311116600761, 152856358784713560205903602973
OFFSET
0,3
FORMULA
G.f.: 1 / (1 - Sum(k>=1} (2*k)!/2 * x^k)).
a(0) = 1; a(n) = Sum_{k=1..n} (2*k)!/2 * a(n-k).
PROG
(PARI) my(N=20, x='x+O('x^N)); Vec(1/(1-sum(k=1, N, (2*k)!/2*x^k)))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Feb 17 2024
STATUS
approved