OFFSET
1,2
COMMENTS
Column 4 of A220738
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 9*a(n-1) -4*a(n-2) -23*a(n-3) -153*a(n-4) +204*a(n-5) +564*a(n-6) -700*a(n-7) +95*a(n-8) +2061*a(n-9) -3000*a(n-10) -4459*a(n-11) +2151*a(n-12) +5800*a(n-13) +320*a(n-14) -1276*a(n-15) -925*a(n-16) +233*a(n-17) +48*a(n-18) +13*a(n-19) -a(n-20)
EXAMPLE
Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
.00.69.49.00...00.69.49.00...00.69.47.00...00.67.49.00...69.47.00.00
.00.00.17.17...69.47.16.14...00.39.16.47...36.47.67.14...39.16.47.00
.00.36.34.00...36.14.00.00...00.00.13.00...36.34.00.00...00.13.00.00
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Dec 18 2012
STATUS
approved