OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Andrásfai Graph
Eric Weisstein's World of Mathematics, Maximal Irredundant Set
Index entries for linear recurrences with constant coefficients, signature (6, -15, 20, -15, 6, -1).
FORMULA
From Eric W. Weisstein, Aug 21 2017: (Start)
a(n) = (-3120 + 10932*n - 4970*n^2 + 765*n^3 - 10*n^4 + 3*n^5)/120 for n > 3.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n > 9.
G.f.: (x (2 - 2 x - 2 x^2 + 30 x^3 - 61 x^4 + 89 x^5 - 112 x^6 + 77 x^7 - 18 x^8))/(-1 + x)^6.
(End)
MATHEMATICA
Table[Piecewise[{{2, n == 1}, {10, n == 2}, {28, n == 3}}, (-3120 + 10932 n - 4970 n^2 + 765 n^3 - 10 n^4 + 3 n^5)/120], {n, 20}]
Join[{2, 10, 28}, LinearRecurrence[{6, -15, 20, -15, 6, -1}, {88, 217, 493, 989, 1794, 3016}, 20]] (* Eric W. Weisstein, Aug 21 2017 *)
CoefficientList[Series[(2 - 2 x - 2 x^2 + 30 x^3 - 61 x^4 + 89 x^5 - 112 x^6 + 77 x^7 - 18 x^8)/(-1 + x)^6, {x, 0, 20}], x] (* Eric W. Weisstein, Aug 21 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Aug 17 2017
EXTENSIONS
a(9)-a(20) from Andrew Howroyd, Aug 19 2017
a(21) and above from Eric W. Weisstein, Aug 21 2017
STATUS
approved