A220620 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly one horizontal, diagonal and antidiagonal neighbor

21, 4565, 624227, 93905509, 13864972277, 2054706174413, 304265433695569, 45062687311719797, 6673721691080067317, 988374130647554935157, 146377412047334158410357, 21678380394232186381827093

Offset

1,1

Comments

Column 7 of A220621

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 201*a(n-1) -6982*a(n-2) -189430*a(n-3) +9590330*a(n-4) -17036302*a(n-5) -2815039392*a(n-6) +24279361760*a(n-7) +198170224768*a(n-8) -2875481635520*a(n-9) -383756692624*a(n-10) +115334410373680*a(n-11) -283314863036560*a(n-12) -1777891655816032*a(n-13) +7541953262286912*a(n-14) +7231319523252480*a(n-15) -67620253084304384*a(n-16) +32587945923607040*a(n-17) +252473367356505600*a(n-18) -301020866429181440*a(n-19) -378989877588835840*a(n-20) +740276347708960768*a(n-21) +102424394439131136*a(n-22) -719256751312953344*a(n-23) +211285473650806784*a(n-24) +277487256139481088*a(n-25) -178573089681702912*a(n-26) -26529867221958656*a(n-27) +59859716422762496*a(n-28) -8012264149876736*a(n-29) -11308640300433408*a(n-30) +1932970382327808*a(n-31) +1107369538879488*a(n-32) -185816928223232*a(n-33) -37457215094784*a(n-34) -13028783292416*a(n-35) +6240587481088*a(n-36) -274877906944*a(n-37)

Example

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

Crossrefs

Sequence in context: A200998 A209473 A055416 * A221120 A203370 A232344

Adjacent sequences: A220617 A220618 A220619 * A220621 A220622 A220623

Keyword

nonn

Author

R. H. Hardin Dec 17 2012

Status

approved