login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A027782 a(n) = 9*(n+1)*binomial(n+2,9)/2. 1
36, 405, 2475, 10890, 38610, 117117, 315315, 772200, 1750320, 3719430, 7482618, 14360580, 26453700, 47006190, 80901810, 135326664, 220641300, 351511875, 548358525, 839188350, 1261890630, 1867083075, 2721610125, 3912807600, 5553662400, 7789011516, 10802941380 (list; graph; refs; listen; history; text; internal format)
OFFSET

7,1

LINKS

T. D. Noe, Table of n, a(n) for n = 7..1000

FORMULA

Number of 12-subsequences of [ 1, n ] with just 2 contiguous pairs;

g.f.: 9*(4+x)*x^7/(1-x)^11.

a(n) = Binomial(n+1, 8)*binomial(n+2, 2). - Zerinvary Lajos, Apr 28 2005, corrected by R. J. Mathar, Feb 13 2016

MATHEMATICA

Table[9*(n + 1)*Binomial[n + 2, 9]/2, {n, 7, 40}] (* Stefan Steinerberger, Apr 09 2006 *)

PROG

(MAGMA) [9*(n+1)*Binomial(n+2, 9)/2: n in [7..33]]; // Vincenzo Librandi, Aug 26 2015

CROSSREFS

Sequence in context: A264361 A055862 A105095 * A179099 A181685 A183353

Adjacent sequences:  A027779 A027780 A027781 * A027783 A027784 A027785

KEYWORD

nonn,easy

AUTHOR

thi ngoc dinh (via R. K. Guy)

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 18 01:16 EDT 2021. Contains 345098 sequences. (Running on oeis4.)