A220725 - OEIS

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A220725

T(n,k)=Number of ways to reciprocally link elements of an nXk array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors

1, 1, 1, 1, 2, 1, 1, 7, 4, 1, 1, 21, 30, 8, 1, 1, 68, 230, 126, 16, 1, 1, 221, 1819, 2586, 534, 32, 1, 1, 717, 14466, 52189, 29310, 2275, 64, 1, 1, 2330, 114900, 1071230, 1485872, 331589, 9667, 128, 1, 1, 7571, 913187, 21914482, 78144195, 42378036, 3751888

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

1,5

COMMENTS

Table starts

.1....1........1...........1..............1................1.................1

.1....2........7..........21.............68..............221...............717

.1....4.......30.........230...........1819............14466............114900

.1....8......126........2586..........52189..........1071230..........21914482

.1...16......534.......29310........1485872.........78144195........4067687187

.1...32.....2275......331589.......42378036.......5717794568......759141297226

.1...64.....9667.....3751888.....1208447287.....418227762771...141539684300104

.1..128....41089....42452438....34459871148...30590627951201.26392338517041335

.1..256...174660...480346122...982649830527.2237516237251959

.1..512...742428..5435081884.28021037742705

.1.1024..3155820.61497557384

.1.2048.13414405

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..111

EXAMPLE

Some solutions for n=3 k=4 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)

.00.67.49.00...00.00.67.47...00.00.67.47...00.79.67.47...00.67.49.00

.39.00.79.17...69.34.37.00...00.39.37.00...39.39.13.00...36.47.00.17

.00.13.36.14...00.13.00.00...00.36.14.00...00.16.14.00...36.46.34.00

CROSSREFS

Column 2 is A000079(n-1)

Sequence in context: A144510 A143670 A169730 * A333142 A196832 A005450

Adjacent sequences: A220722 A220723 A220724 * A220726 A220727 A220728

KEYWORD

nonn,tabl

AUTHOR

R. H. Hardin Dec 18 2012

STATUS

approved