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A274873 Number of set partitions of [n] into exactly nine blocks such that all odd elements are in blocks with an odd index and all even elements are in blocks with an even index. 2
1, 4, 70, 280, 2919, 11676, 94944, 379776, 2669361, 10677444, 68321994, 273287976, 1640345707, 6561382828, 37643205652, 150572822608, 836008721925, 3344034887700, 18122573826942, 72490295307768, 385781480224959, 1543125920899836, 8099850233307144 (list; graph; refs; listen; history; text; internal format)
OFFSET

9,2

LINKS

Alois P. Heinz, Table of n, a(n) for n = 9..1000

FORMULA

G.f.: x^9/((x-1)*(3*x-1)*(2*x+1)*(2*x-1)*(3*x+1)*(4*x-1)*(x+1)* (12*x^2-1)*(6*x^2-1)*(20*x^2-1)*(2*x^2-1)).

EXAMPLE

a(9) = 1: 1|2|3|4|5|6|7|8|9.

a(10) = 4: 1|2(10)|3|4|5|6|7|8|9, 1|2|3|4(10)|5|6|7|8|9, 1|2|3|4|5|6(10)|7|8|9, 1|2|3|4|5|6|7|8(10)|9.

CROSSREFS

Column k=9 of A274537.

Sequence in context: A308294 A278553 A101841 * A281654 A222309 A061609

Adjacent sequences:  A274870 A274871 A274872 * A274874 A274875 A274876

KEYWORD

nonn,easy

AUTHOR

Alois P. Heinz, Jul 09 2016

STATUS

approved

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Last modified November 30 20:17 EST 2021. Contains 349425 sequences. (Running on oeis4.)