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

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A055797 T(2n+4,n), array T as in A055794. 4
1, 6, 22, 64, 162, 372, 792, 1584, 3003, 5434, 9438, 15808, 25636, 40392, 62016, 93024, 136629, 196878, 278806, 388608, 533830, 723580, 968760, 1282320, 1679535, 2178306, 2799486, 3567232, 4509384 (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>=7, a(n-7) is the number of 7-subsets of X which do not have exactly one element in common with Y. - Milan Janjic, Dec 28 2007

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Alexsandar Petojevic, The Function vM_m(s; a; z) and Some Well-Known Sequences, Journal of Integer Sequences, Vol. 5 (2002), Article 02.1.7

Index entries for linear recurrences with constant coefficients, signature (8,-28,56,-70,56,-28,8,-1).

FORMULA

a(n-5) = binomial(n,7) + binomial(n,5) for n>4. - Zerinvary Lajos, Jul 24 2006

G.f.: (1-2*x+2*x^2)/(1-x)^8. - Colin Barker, Feb 22 2012

a(n) = 8*(n-1) - 28*(n-2) + 56*(n-3) - 70*(n-4) + 56*(n-5) - 28*(n-6) + 8*(n-7) - (n-8). - Vincenzo Librandi, May 01 2012

a(n) = (n+5)*(n+4)*(n+3)*(n+2)*(n+1)*(n^2-n+42)/5040. - R. J. Mathar, Oct 01 2021

MAPLE

[seq(binomial(n, 7)+binomial(n, 5), n=5..34)]; # Zerinvary Lajos, Jul 24 2006

MATHEMATICA

a=1; b=2; c=3; d=4; e=5; f=6; s=7; lst={s}; Do[a+=n; b+=a; c+=b; d+=c; e+=d; f+=e; s+=f; AppendTo[lst, s], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, May 24 2009 *)

CoefficientList[Series[(1-2*x+2*x^2)/(1-x)^8, {x, 0, 30}], x] (* Vincenzo Librandi, May 01 2012 *)

PROG

(Magma) [Binomial(n, 7) + Binomial(n, 5): n in [5..40]]; // Vincenzo Librandi, May 01 2012

CROSSREFS

Cf. A051601.

Sequence in context: A120477 A053739 A280481 * A001925 A002663 A099855

Adjacent sequences: A055794 A055795 A055796 * A055798 A055799 A055800

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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 3 09:50 EST 2022. Contains 358517 sequences. (Running on oeis4.)