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 A228484 a(n) = 2^n*(3*n)!/(n!*(2*n)!). 2
 1, 6, 60, 672, 7920, 96096, 1188096, 14883840, 188280576, 2399654400, 30766095360, 396363202560, 5126871859200, 66538909237248, 866061993246720, 11300615801536512, 147773778404769792, 1936073567335219200, 25408660721789829120, 333963051307735449600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Oblique diagonal of the Pell-Jacobsthal triangle A013609. Its mirror diagonal is A006588. Asymptotic approximation of a(n) ~ C*(13.5)^n/sqrt(n) with C = (1/2)*sqrt(3/Pi) = A137209. LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..200 FORMULA a(n) = 2^n*A005809(n). a(n) = A013609(3*n, n). a(n) = A006588(n)/2^n. a(n) = (2*n+1)*A153231(n). MAPLE a := n -> 2^n*binomial(3*n, n): seq(a(n), n=0..16); MATHEMATICA Table[2^n (3 n)!/(n! (2 n)!), {n, 0, 20}] (* Vincenzo Librandi, Aug 24 2013 *) PROG (MAGMA) [2^n*Factorial(3*n)/(Factorial(n)*Factorial(2*n)): n in [0..20]]; // Vincenzo Librandi, Aug 24 2013 CROSSREFS Cf. A013609, A006588. Sequence in context: A295503 A106259 A085364 * A232969 A232246 A086984 Adjacent sequences:  A228481 A228482 A228483 * A228485 A228486 A228487 KEYWORD nonn,easy AUTHOR Johannes W. Meijer, Aug 22 2013 EXTENSIONS More terms from Vincenzo Librandi, Aug 24 2013 STATUS approved

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Last modified August 23 22:45 EDT 2019. Contains 326254 sequences. (Running on oeis4.)