A123821 Number of ways to build a contiguous building with n LEGO blocks of size 2 X 2 on top of a fixed block of the same size.

9, 97, 1349, 20288, 329707, 5574248, 97506021, 1747201171, 31923371982, 592403479154

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..10.

Crossrefs

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

Sequence in context: A194725 A218500 A293986 * A145509 A098782 A076758

Adjacent sequences: A123818 A123819 A123820 * A123822 A123823 A123824

Keyword

nonn,hard

Author

Søren Eilers, Oct 29 2006

Status

approved