A027086 a(n) = A027082(n, n+4).

11, 41, 108, 246, 517, 1035, 2010, 3828, 7199, 13429, 24920, 46090, 85065, 156791, 288758, 531528, 978099, 1799521, 3310404, 6089406, 11200845, 20602307, 37894354, 69699452, 128198215, 235794285, 433694384, 797689490, 1467180945, 2698567791, 4963441390

Offset: 4

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

• Colin Barker, Table of n, a(n) for n = 4..1000
• Index entries for linear recurrences with constant coefficients, signature (4,-5,2,-1,2,-1).

Crossrefs

Cf. A027026, A027082.

Programs

Magma

I:=[11,41,108,246,517,1035]; [n le 6 select I[n] else 4*Self(n-1)-5*Self(n-2)+2*Self(n-3)-Self(n-4)+2*Self(n-5)-Self(n-6): n in [1..40]]; // Vincenzo Librandi, Feb 20 2016

Mathematica

LinearRecurrence[{4, -5, 2, -1, 2, -1}, {11, 41, 108, 246, 517, 1035}, 35] (* Vincenzo Librandi, Feb 20 2016 *)

PARI

Vec(x^4*(11-3*x-x^2-3*x^3+2*x^4)/((1-x)^3*(1-x-x^2-x^3)) + O(x^40)) \\ Colin Barker, Feb 20 2016

Formula

a(n) = A027026(n) + (n+1)(n+2)/2 - 3.

From Colin Barker, Feb 20 2016: (Start)

a(n) = 4*a(n-1)-5*a(n-2)+2*a(n-3)-a(n-4)+2*a(n-5)-a(n-6) for n>9.

G.f.: x^4*(11-3*x-x^2-3*x^3+2*x^4) / ((1-x)^3*(1-x-x^2-x^3)).

(End)

a(n) = A000213(n+4) -4 -3*n*(n+3)/2. - R. J. Mathar, Jun 24 2020