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A318161 Number of compositions of 2n into exactly 2n nonnegative parts with largest part n. 3
1, 1, 18, 195, 1652, 12825, 96030, 705341, 5116200, 36773397, 262462010, 1862790699, 13160496684, 92624149475, 649794035142, 4545979700445, 31727803153232, 220975193536845, 1536191185018770, 10661898343645847, 73890140441316420, 511405029708269529 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
FORMULA
a(n) = A180281(2n,n).
For n>0, a(n) = n - 2*n^2 + 2*n*binomial(3*n - 2, n). - Vaclav Kotesovec, Sep 20 2019
EXAMPLE
a(2) = 18: 0022, 0112, 0121, 0202, 0211, 0220, 1012, 1021, 1102, 1120, 1201, 1210, 2002, 2011, 2020, 2101, 2110, 2200.
MATHEMATICA
Flatten[{1, Table[n - 2*n^2 + 2*n*Binomial[3*n - 2, n], {n, 1, 20}]}] (* Vaclav Kotesovec, Sep 20 2019 *)
CROSSREFS
Bisection of A318160 (even part).
Cf. A180281.
Sequence in context: A004314 A338099 A125406 * A182311 A181711 A042940
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 19 2018
STATUS
approved

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)