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%I #6 Apr 28 2014 09:24:26
%S 21,150,688,2561,8253,23930,64030,160539,381379,865676,1889308,
%T 3984311,8151834,16234161,31554397,59999259,111824744,204629354,
%U 368190175,652238928,1138836325,1961870558,3337496363,5611246209,9330350788,15353900381,25019429935
%N Number of Carlitz compositions of n with exactly seven descents.
%C No two adjacent parts of a Carlitz composition are equal.
%H Alois P. Heinz, <a href="/A241697/b241697.txt">Table of n, a(n) for n = 21..1000</a>
%p b:= proc(n, i) option remember; `if`(n=0, 1,
%p convert(series(add(`if`(i=j, 0, b(n-j, j)*
%p `if`(j<i, x, 1)), j=1..n), x, 8), polynom))
%p end:
%p a:= n-> coeff(b(n, 0), x, 7):
%p seq(a(n), n=21..50);
%Y Column k=7 of A241701.
%K nonn
%O 21,1
%A _Alois P. Heinz_, Apr 27 2014
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