A077046 - OEIS

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A077046

Doubly restricted composition numbers: number of compositions of [n^2/2] into exactly n positive integers each strictly less than n.

0, 1, 3, 19, 155, 1751, 24017, 398567, 7635987, 167729959, 4123838279, 112835748609, 3386455204288, 110976634957761, 3932912125462725, 150186639579545295, 6137695417757646851, 267654541150392845543, 12391407810082341898091, 607584722159224093306229

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OFFSET

1,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..70

Index entries for sequences related to compositions

FORMULA

a(n) = A077042(n-1, n).

a(n) ~ exp(-1)*sqrt(6/Pi)*n^(n-3/2). - Vaclav Kotesovec, Mar 26 2016

EXAMPLE

a(3) = 3 since the compositions of [3^2/2]=4 into exactly 3 positive integers each strictly less than 3 are: 1+1+2, 1+2+1 and 2+1+1.

CROSSREFS