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!)
A151647 Number of permutations of 5 indistinguishable copies of 1..n with exactly 2 adjacent element pairs in decreasing order. 2
0, 100, 5925, 167475, 3882250, 84320250, 1791011475, 37753995925, 793816473600, 16676797204500, 350257183908625, 7355694727665975, 154471515733316550, 3243914368665860350, 68122282848892857375, 1430568461732082827625, 30041941039388979651100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..500

FORMULA

a(n) = 21^n - (5*n + 1)*6^n + 5*n*(5*n + 1)/2. - Andrew Howroyd, May 06 2020

PROG

(PARI) a(n) = {21^n - (5*n + 1)*6^n + 5*n*(5*n + 1)/2} \\ Andrew Howroyd, May 06 2020

CROSSREFS

Column k=2 of A237202.

Sequence in context: A017763 A204081 A053109 * A245666 A210814 A065689

Adjacent sequences:  A151644 A151645 A151646 * A151648 A151649 A151650

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 29 2009

EXTENSIONS

Terms a(8) and beyond from Andrew Howroyd, May 06 2020

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 July 9 11:58 EDT 2020. Contains 335543 sequences. (Running on oeis4.)