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!)
 A005056 a(n) = 3^n + 2^n - 1. 10
 1, 4, 12, 34, 96, 274, 792, 2314, 6816, 20194, 60072, 179194, 535536, 1602514, 4799352, 14381674, 43112256, 129271234, 387682632, 1162785754, 3487832976, 10462450354, 31385253912, 94151567434, 282446313696, 847322163874, 2541932937192, 7625731702714 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Binomial transform of A083313. - Paul Barry, Apr 25 2003 Let P(A) be the power set of an n-element set A and R be a relation on P(A) such that for all x, y of P(A), xRy if either 0) x is a proper subset of y or y is a proper subset of x and x and y are disjoint, 1) x is not a subset of y and y is not a subset of x and x and y are disjoint, or 2) x equals y. Then a(n) = |R|. - Ross La Haye, Mar 19 2009 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Ross La Haye, Binary Relations on the Power Set of an n-Element Set, Journal of Integer Sequences, Vol. 12 (2009), Article 09.2.6. Index entries for linear recurrences with constant coefficients, signature (6,-11,6). FORMULA From Paul Barry, Apr 25 2003: (Start) G.f.: (1-2x-x^2)/((1-x)(1-2x)(1-3x)). E.g.f.: exp(3x) + exp(2x) - exp(x). (End) a(n) = 5*a(n-1) - 6*a(n-2) - 2 for n > 1, a(0)=1, a(1)=4. - Vincenzo Librandi, Dec 31 2010 a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3) for n > 2, a(0)=1, a(1)=4, a(2)=12. - Rick L. Shepherd, Aug 07 2017 MATHEMATICA Table[3^n + 2^n - 1, {n, 0, 60}] (* Vladimir Joseph Stephan Orlovsky, Jun 27 2011 *) CoefficientList[Series[(1 - 2 x - x^2) / ((1 - x) (1 - 2 x) (1 - 3 x)), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 08 2013 *) PROG (PARI) a(n) = 3^n + 2^n - 1 \\ Rick L. Shepherd, Aug 07 2017 CROSSREFS Sequence in context: A173412 A079818 A115390 * A014143 A077994 A077843 Adjacent sequences:  A005053 A005054 A005055 * A005057 A005058 A005059 KEYWORD nonn,easy AUTHOR 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 August 14 04:13 EDT 2020. Contains 336477 sequences. (Running on oeis4.)