OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..200
Eric Weisstein's World of Mathematics, Edge Cover
Eric Weisstein's World of Mathematics, Grid Graph
Eric Weisstein's World of Mathematics, Minimal Edge Cover
FORMULA
Empirical: a(n) = 3*a(n-1)+6*a(n-2)+35*a(n-3) -7*a(n-4)+15*a(n-5)-55*a(n-6) +31*a(n-7)+36*a(n-8)+36*a(n-9) -124*a(n-10)-8*a(n-12)+32*a(n-13) +a(n-14)+9*a(n-15)-2*a(n-16) -2*a(n-17)-a(n-18) for n>18.
Empirical g.f.: x*(1 + 3*x + 14*x^2 + 5*x^3 + 20*x^4 - 12*x^5 + 15*x^6 + 6*x^7 + 2*x^8 - 82*x^9 - 5*x^10 - 3*x^11 + 29*x^12 + 8*x^14 - 2*x^15 - 2*x^16 - x^17) / (1 - 3*x - 6*x^2 - 35*x^3 + 7*x^4 - 15*x^5 + 55*x^6 - 31*x^7 - 36*x^8 - 36*x^9 + 124*x^10 + 8*x^12 - 32*x^13 - x^14 - 9*x^15 + 2*x^16 + 2*x^17 + x^18). - Colin Barker, Jun 16 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Jun 04 2017
STATUS
approved