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A026005
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a(n) = T(4n,n), where T = Catalan triangle (A008315).
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0
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1, 4, 27, 208, 1700, 14364, 123970, 1085760, 9612108, 85795600, 770755843, 6960408624, 63127818572, 574609830760, 5246348656500, 48027225765120, 440671237120764, 4051508174260272, 37315784743418332
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| (2n+2)/(3n+2) * C(4n+1, n). - R. Stephan, Apr 30 2004
a(n)=C(4n,n)-C(4n,n-2)=A039598(2n,n). [From Paul Barry (pbarry(AT)wit.ie), Apr 21 2009]
G.f.: (g-2)*g^2/(3*g-4) where g = 1+x*g^4 is the g.f. of A002293 - Mark van Hoeij, Nov 11 2011
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PROG
| (PARI) (2*n+2)/(3*n+2)*binomial(4*n+1, n)
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CROSSREFS
| Sequence in context: A091125 A193221 A091121 * A059391 A190738 A160883
Adjacent sequences: A026002 A026003 A026004 * A026006 A026007 A026008
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KEYWORD
| nonn
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AUTHOR
| Clark Kimberling (ck6(AT)evansville.edu)
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EXTENSIONS
| More terms from R. Stephan, Apr 30 2004
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