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A052773
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A simple grammar.
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0
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1, 1, 5, 31, 229, 1832, 15583, 137791, 1255202, 11693697, 110905169, 1067181020, 10392861567, 102239342761, 1014484221699, 10141596951782, 102044286177390, 1032652191535027, 10503201188806574, 107313868098732336, 1100922685481490057, 11335843298568212815, 117111555943587032146, 1213575764038590524010
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 730
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FORMULA
| G.f.: A(x) = exp(A(x)^4*x + A(x^2)^4*x^2/2 + A(x^3)^4*x^3/3 +...), A(0)=1; also, A(x)^4 = sum_{n=0..inf} A052763(n+1)x^n. - Paul D. Hanna (pauldhanna(AT)juno.com), Jul 13 2006
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MAPLE
| spec := [S, {S=Set(B), B=Prod(Z, S, S, S, S)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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PROG
| (PARI) {a(n)=local(A=1+x+x*O(x^n)); if(n==0, 1, for(i=1, n, A=exp(sum(k=1, n, subst(x*A^4, x, x^k+x*O(x^n))/k))); polcoeff(A, n, x))} - Paul D. Hanna (pauldhanna(AT)juno.com), Jul 13 2006
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CROSSREFS
| Cf. A052763.
Sequence in context: A058309 A192950 A001910 * A062147 A069321 A177797
Adjacent sequences: A052770 A052771 A052772 * A052774 A052775 A052776
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KEYWORD
| easy,nonn
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AUTHOR
| encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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EXTENSIONS
| More terms from Paul D. Hanna (pauldhanna(AT)juno.com), Jul 13 2006
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