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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A328890 Number of acyclic edge covers of the complete bipartite graph K_{n,2}. 2
 1, 6, 18, 46, 110, 254, 574, 1278, 2814, 6142, 13310, 28670, 61438, 131070, 278526, 589822, 1245182, 2621438, 5505022, 11534334, 24117246, 50331646, 104857598, 218103806, 452984830, 939524094, 1946157054, 4026531838, 8321499134, 17179869182, 35433480190, 73014444030 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..1000 Eric Weisstein's World of Mathematics, Complete Bipartite Graph Index entries for linear recurrences with constant coefficients, signature (5,-8,4). FORMULA a(n) = 2*A000225(n-1) + A001787(n). a(n) = (2 + n)*2^(n-1) - 2. From Colin Barker, Nov 05 2019: (Start) G.f.: x*(1 + x - 4*x^2) / ((1 - x)*(1 - 2*x)^2). a(n) = 5*a(n-1) - 8*a(n-2) + 4*a(n-3) for n>3. (End) PROG (PARI) a(n) = {(2 + n)*2^(n-1) - 2} (PARI) Vec(x*(1 + x - 4*x^2) / ((1 - x)*(1 - 2*x)^2) + O(x^30)) \\ Colin Barker, Nov 05 2019 CROSSREFS Column 2 of A328888. Cf. A000225, A001787. Sequence in context: A031128 A304161 A261016 * A188379 A299268 A248462 Adjacent sequences: A328887 A328888 A328889 * A328891 A328892 A328893 KEYWORD nonn,easy AUTHOR Andrew Howroyd, Oct 29 2019 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 21 11:17 EDT 2024. Contains 371853 sequences. (Running on oeis4.)