A220722 Number of ways to reciprocally link elements of an nX5 array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors

1, 68, 1819, 52189, 1485872, 42378036, 1208447287, 34459871148, 982649830527, 28021037742705, 799042082604660, 22785317589182003, 649741368852004381, 18527889499243277120, 528337436670523419632, 15065960264863439367995

Offset

1,2

Comments

Column 5 of A220725

Links

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

Formula

Empirical: a(n) = 24*a(n-1) +104*a(n-2) +571*a(n-3) +3582*a(n-4) +7794*a(n-5) +4788*a(n-6) -16926*a(n-7) -90288*a(n-8) -168845*a(n-9) -84443*a(n-10) +109179*a(n-11) +193126*a(n-12) +248993*a(n-13) +425415*a(n-14) +384428*a(n-15) +353459*a(n-16) +31964*a(n-17) -136170*a(n-18) -85703*a(n-19) -29195*a(n-20) +14155*a(n-21) +6903*a(n-22) +243*a(n-23) -252*a(n-24) -25*a(n-25)

Example

Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
.69.47.69.46.47...69.47.00.69.47...00.69.46.46.47...00.69.46.49.00
.39.19.00.13.00...39.16.47.36.14...00.69.14.37.00...00.00.16.46.14
.00.16.14.00.00...00.13.00.00.00...00.00.13.00.00...00.00.00.00.00

Crossrefs

Sequence in context: A337962 A231106 A228332 * A017784 A035802 A035729

Adjacent sequences: A220719 A220720 A220721 * A220723 A220724 A220725

Keyword

nonn

Author

R. H. Hardin Dec 18 2012

Status

approved