A057818 - OEIS

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

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OFFSET

1,3

LINKS

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

KEYWORD

nonn,nice,more

AUTHOR

EXTENSIONS

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

STATUS

approved