This site is supported by donations to The OEIS Foundation.

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A055799 T(2n+6,n), array T as in A055794. 2
 1, 8, 37, 130, 385, 1012, 2431, 5434, 11440, 22880, 43758, 80444, 142766, 245480, 410210, 667964, 1062347, 1653608, 2523675, 3782350, 5574855, 8090940, 11575785, 16342950, 22789650, 31414656, 42839148, 57830872 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS If Y is a 2-subset of an n-set X then, for n>=9, a(n-9) is the number of 9-subsets of X which have no exactly one element in common with Y. - Milan Janjic, Dec 28 2007 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (10,-45,120,-210,252,-210,120,-45,10,-1). FORMULA a(n-9) = binomial(n,9) - 2*binomial(n-2,8), n=9, 10, ... . - Milan Janjic, Dec 28 2007 G.f.: (1-2*x+2*x^2)/(1-x)^10. - Colin Barker, Feb 21 2012 a(n) = 10*a(n-1) - 45*a(n-2) + 120*a(n-3) - 210*a(n-4)+ 252*a(n-5) - 210*a(n-6) + 120*a(n-7) - 45*a(n-8) + 10*a(n-9) - a(n-10). - Vincenzo Librandi, May 01 2012 MATHEMATICA a=1; b=2; c=3; d=4; e=5; f=6; g=7; s=8; lst={1, s}; Do[a+=n; b+=a; c+=b; d+=c; e+=d; f+=e; g+=f; s+=g; AppendTo[lst, s], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, May 24 2009 *) CoefficientList[Series[(1-2*x+2*x^2)/(1-x)^10, {x, 0, 30}], x] (* Vincenzo Librandi, May 01 2012 *) PROG (MAGMA) [Binomial(n, 9)-2*Binomial(n-2, 8):n in [9..40]]; // Vincenzo Librandi, May 01 2012 CROSSREFS Cf. A051601. Sequence in context: A001780 A258476 A053296 * A035038 A240188 A256412 Adjacent sequences:  A055796 A055797 A055798 * A055800 A055801 A055802 KEYWORD nonn,easy AUTHOR Clark Kimberling, May 28 2000 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.