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A220898
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Number of primitive maps on n edges.
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1
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2, 1, 1, 3, 9, 32, 122, 494, 2088, 9130, 41018, 188420, 881718, 4191343, 20194345, 98442879, 484826387, 2409437854, 12070883798, 60910296202, 309356790766, 1580443960788, 8117428327384, 41896435989770, 217209722907220, 1130759644970931, 5908990116854607, 30987487474146447, 163034985804927311
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OFFSET
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0,1
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LINKS
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FORMULA
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G.f.: A(x/(1+x)), where A(x) is g.f. for A000139.
Conjecture: 2*(n+1)*(2*n+1)*a(n) +(-15*n^2+19*n-8)*a(n-1) -2*(21*n-22)*(n-2)*a(n-2) -23*(n-2)*(n-3)*a(n-3)=0. - R. J. Mathar, May 30 2014
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MATHEMATICA
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A[x_] = (2/(3x)) (HypergeometricPFQ[{-2/3, -1/3}, {1/2}, (27/4) x] - 1);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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