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 A034689 a(n) = n-th sextic factorial number divided by 2. 13
 1, 8, 112, 2240, 58240, 1863680, 70819840, 3116072960, 155803648000, 8725004288000, 540950265856000, 36784618078208000, 2722061737787392000, 217764939022991360000, 18727784755977256960000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA 2*a(n) = (6*n-4)(!^6) = product_{j=1..n} (6*j-4) = 2^n*A007559(n), A007559(n) = (3*n-2)(!^3) = product_{j=1..n} (3*j-2). E.g.f. (-1 + (1-6*x)^(-1/3))/2). D-finite with recurrence: a(n) +2*(-3*n+2)*a(n-1)=0. - R. J. Mathar, Feb 24 2020 MATHEMATICA s=1; lst={s}; Do[s+=n*s; AppendTo[lst, s], {n, 7, 5!, 6}]; lst (* Vladimir Joseph Stephan Orlovsky, Nov 08 2008 *) CROSSREFS Cf. A008542, A007559. Sequence in context: A265665 A302104 A219184 * A010041 A099703 A296467 Adjacent sequences:  A034686 A034687 A034688 * A034690 A034691 A034692 KEYWORD easy,nonn AUTHOR STATUS approved

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Last modified October 26 23:01 EDT 2020. Contains 338033 sequences. (Running on oeis4.)