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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A082679 Number of Lego towers, one piece per floor, where every floor is perpendicular to the one below it (so we have a kind of 3-dimensional zigzag pattern). 1
0, 1, 2, 6, 20, 69, 241, 845, 2966, 10414, 36568, 128409, 450913, 1583401, 5560186, 19524854, 68562444, 240760253, 845440977, 2968805845, 10425101678, 36608235998, 128551546480, 451414815601, 1585164405441 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..24.

D. Zeilberger, [math/9801016] Automated counting of LEGO towers

FORMULA

G.f.: x*(1-3*x+2*x^2-x^3)/(1-5*x+6*x^2-3*x^3+x^4).

MATHEMATICA

CoefficientList[Series[x*(1 - 3*x + 2*x^2 - x^3)/(1 - 5*x + 6*x^2 - 3*x^3 + x^4), {x, 0, 30}], x] (* Wesley Ivan Hurt, Feb 12 2017 *)

CROSSREFS

Sequence in context: A150121 A150122 A150123 * A094854 A217782 A026029

Adjacent sequences:  A082676 A082677 A082678 * A082680 A082681 A082682

KEYWORD

nonn,easy

AUTHOR

Ralf Stephan, May 19 2003

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 April 18 22:08 EDT 2019. Contains 322237 sequences. (Running on oeis4.)