login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A026388 a(n) = number of integer strings s(0),...,s(n) counted by array T in A026386 that have s(n)=2; also a(n) = T(2n,n-1). 1
1, 5, 24, 114, 541, 2573, 12275, 58747, 282003, 1357407, 6549906, 31675020, 153481299, 745011075, 3622111560, 17635418730, 85975792075, 419644943495, 2050493623760, 10029194506990, 49098707209695, 240568930012575 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..22.

Emeric Deutsch, Emanuele Munarini, Simone Rinaldi, Skew Dyck paths, area, and superdiagonal bargraphs, Journal of Statistical Planning and Inference, Vol. 140, Issue 6, June 2010, pp. 1550-1562. Table 1, y_n.

László Németh, Tetrahedron trinomial coefficient transform, arXiv:1905.13475 [math.CO], 2019.

FORMULA

a(n) = hypergeom([3/2, 2, 1-n], [1, 3], -4). - Vladimir Reshetnikov, Apr 25 2016

Conjecture: -(n+1)*(2*n-1)*a(n) +(12*n^2-2*n+1)*a(n-1) -5*(2*n+1)*(n-2)*a(n-2)=0. - R. J. Mathar, Jun 21 2018

MATHEMATICA

Table[HypergeometricPFQ[{3/2, 2, 1-n}, {1, 3}, -4], {n, 1, 20}] (* Vladimir Reshetnikov, Apr 25 2016 *)

CROSSREFS

Sequence in context: A141223 A289783 A140766 * A242509 A057969 A004254

Adjacent sequences:  A026385 A026386 A026387 * A026389 A026390 A026391

KEYWORD

nonn

AUTHOR

Clark Kimberling

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 October 23 17:32 EDT 2019. Contains 328373 sequences. (Running on oeis4.)