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A101600
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G.f.: c(3x)^2, c(x) the g.f. of A000108.
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2
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1, 6, 45, 378, 3402, 32076, 312741, 3127410, 31899582, 330595668, 3471254514, 36848701764, 394807518900, 4263921204120, 46370143094805, 507343918566690, 5580783104233590, 61682339573108100, 684673969261499910
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| G.f.: 4/(1+sqrt(1-12x))^2; a(n)=3^n*A000108(n+1).
(n+2)*a(n) -6*(2*n+1)*a(n-1)=0. - R. J. Mathar, Nov 15 2011
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MAPLE
| Z[0]:=1: for k to 30 do Z[k]:=simplify(1/(1-3*z*Z[k-1])) od: g:=sum((Z[j]-Z[j-1]), j=1..30): gser:=series(g, z=0, 27): seq(coeff(gser, z, n)/3, n=1..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 21 2008
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CROSSREFS
| Cf. A050159, A101601, A101602.
Sequence in context: A153399 A007194 A025551 * A135148 A137974 A001879
Adjacent sequences: A101597 A101598 A101599 * A101601 A101602 A101603
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Dec 08 2004
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