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A240744
Number of compositions of n having exactly nine fixed points.
3
1, 1, 3, 7, 16, 35, 76, 162, 342, 715, 1474, 3049, 6245, 12746, 25922, 52571, 106353, 214731, 432827, 871240, 1751725, 3518787, 7062725, 14167004, 28402284, 56916681, 114017164, 228335406, 457163368, 915131854, 1831578490, 3665302380, 7334102844, 14673905376
OFFSET
45,3
LINKS
Joerg Arndt and Alois P. Heinz, Table of n, a(n) for n = 45..1000
FORMULA
a(n) ~ c * 2^n, where c = 0.00000000000004863374631933235641619389991611011374568106537836728124272498... . - Vaclav Kotesovec, Sep 07 2014
MAPLE
b:= proc(n, i) option remember; `if`(n=0, 1, series(
add(b(n-j, i+1)*`if`(i=j, x, 1), j=1..n), x, 10))
end:
a:= n-> coeff(b(n, 1), x, 9):
seq(a(n), n=45..80);
MATHEMATICA
b[n_, i_] := b[n, i] = If[n == 0, 1, Series[Sum[b[n - j, i + 1]*If[i == j, x, 1], {j, 1, n}], {x, 0, 10}]]; a[n_] := SeriesCoefficient[b[n, 1], {x, 0, 9}]; Table[a[n], {n, 45, 80}] (* Jean-François Alcover, Nov 06 2014, after Maple *)
CROSSREFS
Column k=9 of A238349 and of A238350.
Sequence in context: A240741 A240742 A240743 * A240745 A227682 A099325
KEYWORD
nonn
AUTHOR
Joerg Arndt and Alois P. Heinz, Apr 11 2014
STATUS
approved