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Expansion of (1 - x)^(-2) * Sum_{j>=0} (x^j / (1 - Sum_{k=1..j} x^k)).
2

%I #7 Jan 22 2024 00:04:45

%S 1,3,7,14,26,46,80,138,239,417,735,1309,2355,4275,7823,14416,26728,

%T 49820,93300,175454,331170,627154,1191204,2268604,4330915,8286101,

%U 15884857,30507175,58686513,113066033,218137531,421391695,814999229,1578000229,3058458885,5933549906

%N Expansion of (1 - x)^(-2) * Sum_{j>=0} (x^j / (1 - Sum_{k=1..j} x^k)).

%C Considering more generally the family of generating functions (1 - x)^n * Sum_{j>=0} (x^j / (1 - Sum_{k=1..j} x^k)) one finds several sequences related to compositions as indicated in the cross-references.

%F Partial sums of A186537 starting at n = 1.

%p gf := (1 - x)^(-2) * add(x^j / (1 - add(x^k, k = 1..j)), j = 0..42):

%p ser := series(gf, x, 40): seq(coeff(ser, x, k), k = 0..38);

%Y Cf. This sequence (n=-2), A186537 left shifted (n=-1), A079500 (n=0), A368279 (n=1), A369116 (n=2).

%K nonn

%O 0,2

%A _Peter Luschny_, Jan 21 2024