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A024496
a(n) = (3/(8n-4))*C(4n,n).
0
3, 7, 33, 195, 1292, 9177, 68310, 525915, 4153380, 33460284, 273904969, 2271800037, 19050406788, 161242554550, 1375709203260, 11819200090635, 102162535941492, 887830494976788, 7752586858050900, 67986848888695660, 598522586288243760, 5287559893638230385
OFFSET
1,1
FORMULA
G.f.: (g+2)*(g-1)/g^2 where g = 1+x*g^4 is the g.f. of A002293. - Mark van Hoeij, Nov 11 2011
a(n) ~ 2^(8*n - 5/2) / (sqrt(Pi) * n^(3/2) * 3^(3*n - 1/2)). - Vaclav Kotesovec, Mar 12 2019
MATHEMATICA
Table[3/(8*n - 4)*Binomial[4*n, n], {n, 1, 20}] (* Vaclav Kotesovec, Mar 12 2019 *)
PROG
(PARI) a(n) = 3*binomial(4*n, n)/(8*n-4); \\ Michel Marcus, Mar 12 2019
CROSSREFS
Cf. A005810.
Sequence in context: A054935 A208989 A358961 * A081890 A192880 A355156
KEYWORD
nonn
EXTENSIONS
More terms from Vaclav Kotesovec, Mar 12 2019
STATUS
approved