A220636 Number of ways to reciprocally link elements of an 6Xn array either to themselves or to exactly two horizontal or antidiagonal neighbors

1, 1, 13, 351, 8560, 183961, 3817452, 79063898, 1643423543, 34184820039, 711142299027, 14793696906106, 307746212613995, 6401868705356519, 133174202661890384, 2770341001987547086, 57629691849567578540

Offset

1,3

Comments

Row 6 of A220632

Links

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

Formula

Empirical: a(n) = 32*a(n-1) -195*a(n-2) -1350*a(n-3) +10665*a(n-4) +31692*a(n-5) -206199*a(n-6) -507142*a(n-7) +1799954*a(n-8) +4606048*a(n-9) -7358332*a(n-10) -21711948*a(n-11) +13920815*a(n-12) +54513592*a(n-13) -9084809*a(n-14) -73913886*a(n-15) -4653883*a(n-16) +53601160*a(n-17) +7698097*a(n-18) -21029870*a(n-19) -3072503*a(n-20) +4411176*a(n-21) +533603*a(n-22) -476894*a(n-23) -41967*a(n-24) +24240*a(n-25) +1155*a(n-26) -450*a(n-27) for n>32

Example

Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)
.00.67.47...00.67.47...00.67.47...00.00.00...00.00.00...00.00.00...00.67.47
.36.34.00...36.34.00...36.34.00...00.67.47...00.00.00...00.00.00...36.34.00
.00.00.00...00.67.47...00.00.00...36.34.00...00.67.47...00.67.47...00.00.00
.00.00.00...36.34.00...00.00.00...00.00.00...36.34.00...36.34.00...00.67.47
.00.67.47...00.00.00...00.00.00...00.00.00...00.67.47...00.00.00...36.34.00
.36.34.00...00.00.00...00.00.00...00.00.00...36.34.00...00.00.00...00.00.00

Crossrefs

Sequence in context: A160396 A253125 A297070 * A078738 A218419 A165391

Adjacent sequences: A220633 A220634 A220635 * A220637 A220638 A220639

Keyword

nonn

Author

R. H. Hardin Dec 17 2012

Status

approved