A220637 Number of ways to reciprocally link elements of an 7Xn array either to themselves or to exactly two horizontal or antidiagonal neighbors.

1, 1, 21, 1081, 49448, 1932695, 72097810, 2685329069, 100377946990, 3759405889469, 140807441642550, 5273589943694582, 197503772671988555, 7396752550237211667, 277016765034509275485, 10374589395033217351070

Offset: 1

Author

R. H. Hardin Dec 17 2012

Keywords

• nonn

Comments

Row 7 of A220632

Examples

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

Links

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

Formula

Empirical: a(n) = 64*a(n-1) -919*a(n-2) -8570*a(n-3) +216353*a(n-4) +531044*a(n-5) -21261655*a(n-6) -32609802*a(n-7) [phone]*a(n-8) [phone]*a(n-9) -39063293438*a(n-10) -92688824988*a(n-11) [phone]*a(n-12) [phone]*a(n-13) -10235971284893*a(n-14) -39686089670614*a(n-15) [phone]*a(n-16) [phone]*a(n-17) -310370552865987*a(n-18) -2718695732195110*a(n-19) [phone]*a(n-20) +12228246476518236*a(n-21) +4161966890556370*a(n-22) -37977869919855064*a(n-23) -22915950784622786*a(n-24) +83551109201976972*a(n-25) +64155355218097920*a(n-26) -133459785405218204*a(n-27) -114791737399493541*a(n-28) +158383696504733072*a(n-29) +141093830957446007*a(n-30) -142389992780977126*a(n-31) -123172425999322826*a(n-32) +98262359403451972*a(n-33) +77694058934774432*a(n-34) -52288937671239360*a(n-35) -35710455324063520*a(n-36) +21366553927398268*a(n-37) +11998414558707900*a(n-38) -6636734211915116*a(n-39) -2945615880166783*a(n-40) +1547201872012720*a(n-41) [phone]*a(n-42) -266869650005278*a(n-43) -67611096067185*a(n-44) [phone]*a(n-45) [phone]*a(n-46) -2975024785990*a(n-47) -380281115163*a(n-48) [phone]*a(n-49) [phone]*a(n-50) -7030915042*a(n-51) -357383528*a(n-52) [phone]*a(n-53) +4153756*a(n-54) -1668248*a(n-55) -18816*a(n-56) +6272*a(n-57) for n>63