OFFSET
0,3
LINKS
N. J. A. Sloane, Transforms
FORMULA
G.f.: 1/(1 - sum(k>0, x^k/(1-x^k+x^(2*k)))). - Vladeta Jovovic, Dec 04 2004
EXAMPLE
a(3)=6 because the compositions of 3 with designated summands are
3', 2'1', 1'2', 1'11, 11'1, 111'.
The composition 1121 corresponds to 1'12'1' and 11'2'1'.
MATHEMATICA
Table[l = Split /@ Flatten[Permutations /@ IntegerPartitions@n, 1];
Total[Table[x = l[[i]]; Product[Length@x[[j]], {j, Length[x]}], {i, Length[l]}]], {n, 0, 15}] (* Robert Price, Jun 07 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Christian G. Bower, Jan 23 2004
STATUS
approved