A123782 Number of ways to build a contiguous building with n LEGO blocks of size 1x4 on top of a fixed block of the same size.

23, 679, 27591, 1227556, 59212274, 2990304700, 156407426393

Offset

1,1

Comments

The base block is not counted among the n and must be the only block in the bottom layer of the building

Links

Table of n, a(n) for n=1..7.

Crossrefs

Cf. A112389, A123762 - A123827, A123829 - A123849.

Sequence in context: A023295 A169596 A142553 * A023278 A013362 A013365

Adjacent sequences: A123779 A123780 A123781 * A123783 A123784 A123785

Keyword

nonn,hard

Author

Søren Eilers, Oct 29 2006

Status

approved