The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A105861 a(n) = (n/2) * Sum_{k=0..n} binomial(n,k)/gcd(n,k). 3
 1, 3, 10, 23, 76, 102, 442, 695, 1792, 2828, 11254, 13334, 53236, 65418, 155110, 347319, 1114096, 1259328, 4980718, 6223148, 15033700, 27548678, 96468970, 108761942, 352992576, 529504212, 1381165192, 2314603370, 7784628196 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS If instead the limits of the summation run from 1 to n-1, then the sum is A105861(n)-1. LINKS Table of n, a(n) for n=1..29. FORMULA a(n) = (n/2) * Sum_{k=0..n} binomial(n, k) / gcd(n, k). MATHEMATICA f[n_] := n*Sum[ Binomial[n, k] / GCD[n, k], {k, 0, n}]/2; Table[ f[n], {n, 30}] PROG (PARI) a(n) = sum(k=0, n, binomial(n, k)/gcd(n, k))*n/2; \\ Michel Marcus, Oct 19 2019 CROSSREFS Cf. A105862, A105863. Sequence in context: A185828 A134438 A092255 * A228493 A041327 A231116 Adjacent sequences: A105858 A105859 A105860 * A105862 A105863 A105864 KEYWORD nonn AUTHOR Robert G. Wilson v, Apr 23 2005 STATUS approved

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

Last modified April 15 05:06 EDT 2024. Contains 371667 sequences. (Running on oeis4.)