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!)
A152500 1/4 the number of permutations of 3 indistinguishable copies of 1..n with exactly 3 local maxima. 1
0, 1, 231, 21490, 1476084, 90050080, 5228286336, 297239712256, 16749407726592, 940343619493888, 52712719000338432, 2953100593082269696, 165399775808105742336, 9262957817232621568000, 518737995604927325405184, 29049593918675470746910720, 1626782962901824260072800256 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..200

Index entries for linear recurrences with constant coefficients, signature (108,-3840,58752,-401664,1244160,-1433600).

FORMULA

From Colin Barker, Jul 19 2020: (Start)

G.f.: x^2*(1 + 123*x + 382*x^2 - 16548*x^3 - 15440*x^4) / ((1 - 4*x)^3*(1 - 20*x)^2*(1 - 56*x)).

a(n) = 108*a(n-1) - 3840*a(n-2) + 58752*a(n-3) - 401664*a(n-4) + 1244160*a(n-5) - 1433600*a(n-6) for n>6.

(End)

PROG

(PARI) \\ PeaksBySig defined in A334774.

a(n) = {PeaksBySig(vector(n, i, 3), [2])[1]/4} \\ Andrew Howroyd, May 12 2020

(PARI) concat(0, Vec(x^2*(1 + 123*x + 382*x^2 - 16548*x^3 - 15440*x^4) / ((1 - 4*x)^3*(1 - 20*x)^2*(1 - 56*x)) + O(x^19))) \\ Colin Barker, Jul 19 2020

CROSSREFS

Cf. A152499, A334774.

Sequence in context: A152102 A183663 A201957 * A066370 A139412 A027551

Adjacent sequences:  A152497 A152498 A152499 * A152501 A152502 A152503

KEYWORD

nonn,easy

AUTHOR

R. H. Hardin, Dec 06 2008

EXTENSIONS

Terms a(10) and beyond from Andrew Howroyd, May 12 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 November 28 13:39 EST 2021. Contains 349412 sequences. (Running on oeis4.)