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A052775
G.f. A(x) satisfies: A(x) = exp( Sum_{k>=1} (-1)^(k+1) * A(x^k)^4 * x^k / k ).
3
1, 1, 4, 26, 184, 1443, 11888, 101859, 897529, 8085103, 74113656, 689134849, 6484074328, 61620879930, 590628242876, 5703027934533, 55423681958153, 541689157201498, 5320989368024126, 52503593913927276
OFFSET
0,3
COMMENTS
Old name was: A simple grammar.
FORMULA
G.f. A(x) satisfies: A(x) = exp( Sum_{k>=1} (-1)^(k+1) * A(x^k)^4 * x^k / k ). - Ilya Gutkovskiy, May 26 2023
MAPLE
spec := [S, {B=Prod(Z, S, S, S, S), S=PowerSet(B)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
New name from Ilya Gutkovskiy, May 26 2023
STATUS
approved