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!)
A027768 a(n) = (n+1)*binomial(n+1,8). 1
8, 81, 450, 1815, 5940, 16731, 42042, 96525, 205920, 413270, 787644, 1436058, 2519400, 4273290, 7034940, 11277222, 17651304, 27039375, 40619150, 59942025, 87026940, 124472205, 175587750, 244550475, 336585600, 458177148, 617310936, 823753700, 1089372240 (list; graph; refs; listen; history; text; internal format)
OFFSET

7,1

COMMENTS

Number of 10-subsequences of [ 1, n ] with just 1 contiguous pair.

1625*a(n) is the number of permutations of (n+1) symbols that 8-commute with an (n+1)-cycle (see A233440 for definition), where 1625 = A000757(8). - Luis Manuel Rivera Martínez, Feb 07 2014

LINKS

Table of n, a(n) for n=7..35.

Luis Manuel Rivera, Integer sequences and k-commuting permutations, arXiv preprint arXiv:1406.3081 [math.CO], 2014-2015.

Index entries for linear recurrences with constant coefficients, signature (10,-45,120,-210,252,-210,120,-45,10,-1).

FORMULA

G.f.: (8+x)*x^7/(1-x)^10.

From Amiram Eldar, Jan 30 2022: (Start)

Sum_{n>=7} 1/a(n) = 48877/3675 - 4*Pi^2/3.

Sum_{n>=7} (-1)^(n+1)/a(n) = 2*Pi^2/3 + 38656*log(2)/105 - 2884681/11025. (End)

MATHEMATICA

Table[(n+1)Binomial[n+1, 8], {n, 7, 40}] (* Harvey P. Dale, Jul 08 2017 *)

PROG

(PARI) a(n) = (n+1)*binomial(n+1, 8); \\ Michel Marcus, Jan 31 2014

CROSSREFS

Cf. A000757, A233440.

Sequence in context: A247536 A302822 A303515 * A236749 A343274 A240480

Adjacent sequences: A027765 A027766 A027767 * A027769 A027770 A027771

KEYWORD

nonn,easy

AUTHOR

Thi Ngoc Dinh (via R. K. Guy)

EXTENSIONS

Incorrect formula deleted . - R. J. Mathar, Feb 13 2016

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 November 27 03:51 EST 2022. Contains 358362 sequences. (Running on oeis4.)