The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A305627 a(n) = (2^n / n!) * (2^1 - 1) * (2^2 - 1) * ... * (2^n - 1). 1
 1, 2, 6, 28, 210, 2604, 54684, 1984248, 126495810, 14364301980, 2938936185108, 1093818612893832, 746531203300040340, 940744167112404680760, 2201744527114646554984440, 9619275055995416488956686064, 78799898849332452450472052650530 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) = b[n, 0, 1] in A157285. LINKS G. C. Greubel, Table of n, a(n) for n = 0..85 FORMULA 0 = +a(n)*(+a(n+1)*(+2*a(n+3)) +a(n+2)*(-6*a(n+2) +a(n+3))) +a(n+1)*(+a(n+1)*(+4*a(n+2) - 4*a(n+3)) +a(n+2)*(+4*a(n+2))) for all n in Z. MATHEMATICA a[ n_] := If[n < 0, 0, QPochhammer[2, 2, n] (-2)^n / n!]; PROG (PARI) {a(n) = if( n<0, 0, prod(k=1, n, 2^k - 1) * 2^n / n!)}; (MAGMA) [1] cat [(&*[(2*k-1): k in [1..n]])*2^n/Factorial(n): n in [1..20]]; // G. C. Greubel, Jul 28 2018 CROSSREFS Cf. A157285. Sequence in context: A272662 A125812 A093657 * A006117 A118025 A226773 Adjacent sequences:  A305624 A305625 A305626 * A305628 A305629 A305630 KEYWORD nonn,easy AUTHOR Michael Somos, Jun 06 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 29 15:17 EDT 2020. Contains 337432 sequences. (Running on oeis4.)