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A052831
A simple grammar.
0
0, 1, 2, 4, 11, 29, 91, 286, 955, 3235, 11240, 39559, 141217, 509059, 1852248, 6790372, 25062536, 93043286, 347223013, 1301777476, 4900835727, 18519492431, 70220471264, 267080436295, 1018708832722, 3895714521787, 14933608764343, 57372586025039, 220869710184189
OFFSET
0,3
FORMULA
G.f. satisfies A(x) = Sum_{j>=1} (phi(j)/j) * log( 1/(1-B(x^j)) ), where B(x) = x * exp( Sum_{j>=1} (-1)^(j+1) * S(x^j) / j ). - Sean A. Irvine, Dec 02 2021
MAPLE
spec := [S, {B=Prod(C, Z), C=PowerSet(S), S=Cycle(B)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
CROSSREFS
Sequence in context: A148145 A052869 A316768 * A339834 A148146 A148147
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
EXTENSIONS
More terms from Sean A. Irvine, Dec 02 2021
STATUS
approved