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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A027806 a(n) = 30*(n+1)*binomial(n+4,10). 1
210, 2640, 17820, 85800, 330330, 1081080, 3123120, 8168160, 19691100, 44341440, 94225560, 190466640, 368588220, 686439600, 1235591280, 2157381600, 3665097150, 6074125200, 9842332500, 15623407800, 24336462150, 37255818600, 56125648800, 83304936000, 121949170200 (list; graph; refs; listen; history; text; internal format)
OFFSET

6,1

COMMENTS

Number of 15-subsequences of [ 1, n ] with just 4 contiguous pairs.

LINKS

T. D. Noe, Table of n, a(n) for n = 6..1000

Index entries for linear recurrences with constant coefficients, signature (12,-66,220,-495,792,-924,792,-495,220,-66,12,-1).

FORMULA

G.f.: 30*(7+4x)*x^6/(1-x)^12.

a(n) = C(n+1, 7)*C(n+4, 4). - Zerinvary Lajos, May 26 2005; corrected by R. J. Mathar, Feb 13 2016

From Amiram Eldar, Feb 03 2022: (Start)

Sum_{n>=6} 1/a(n) = 14*Pi^2/3 - 10444807/226800.

Sum_{n>=6} (-1)^n/a(n) = 7*Pi^2/3 + 3584*log(2)/45 - 2534651/32400. (End)

MATHEMATICA

Table[30 * (n+1) * Binomial[n+4, 10], {n, 6, 50}] (* Amiram Eldar, Feb 03 2022 *)

CROSSREFS

Sequence in context: A135201 A187663 A064260 * A024407 A027822 A024449

Adjacent sequences:  A027803 A027804 A027805 * A027807 A027808 A027809

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 28 07:25 EDT 2022. Contains 354903 sequences. (Running on oeis4.)