OFFSET
4,1
LINKS
Eric Weisstein's World of Mathematics, Irredundant Set
Eric Weisstein's World of Mathematics, Wheel Graph
Index entries for linear recurrences with constant coefficients, signature (2, 0, -1, 1, -1, -1, 1).
FORMULA
a(n)=2*a(n-1)-a(n-3)+a(n-4)-a(n-5)-a(n-6)+a(n-7).
G.f.: -x^4*(5+2*x-7*x^2-4*x^3+x^4-2*x^5+4*x^6) / ( (x-1)*(x^6-x^4-x^2-x+1) ).
MATHEMATICA
Table[1 - RootSum[1 - #^2 - #^4 - #^5 + #^6 &, -2 #^(n + 3) - #^(n + 4) - #^(n + 6) + #^(n + 7) &], {n, 4, 20}]
LinearRecurrence[{2, 0, -1, 1, -1, -1, 1}, {5, 12, 17, 25, 44, 76, 131}, 20]
CoefficientList[Series[(-5 - 2 x + 7 x^2 + 4 x^3 - x^4 + 2 x^5 - 4 x^6)/(-1 + 2 x - x^3 + x^4 - x^5 - x^6 + x^7), {x, 0, 20}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Aug 04 2017
STATUS
approved