A057818 Number of factorable (see A057765 for definition) subsets of a 2 X n uniform grid.

0, 1, 6, 33, 108, 345, 1014, 2865, 7464, 19791, 51286, 133249, 340780, 875487, 2237862, 5804489, 14938614, 38623851, 100015302, 259836689, 674534218

Offset

1,3

Links

Table of n, a(n) for n=1..21.

Sean A. Irvine, Java program (github)

Example

There are six factorable subsets of
[___] namely [11_] [1_1] [_11] [111] [_11] [11_]
[___] ...... [22_] [2_2] [_22] [222] [22_] [_22], so a(3) = 6
(the numerals denote the elements of a particular translated copy).

Crossrefs

See A057765 and A057750.

Sequence in context: A274218 A135526 A204185 * A063267 A082106 A297392

Adjacent sequences: A057815 A057816 A057817 * A057819 A057820 A057821

Keyword

nonn,nice,more

Author

John W. Layman, Nov 07 2000

Extensions

a(13)-a(21) from Sean A. Irvine, Jul 07 2022

Status

approved