OFFSET
4,1
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).
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
MATHEMATICA
LinearRecurrence[{4, -5, 2, -1, 2, -1}, {11, 41, 108, 246, 517, 1035}, 35] (* Vincenzo Librandi, Feb 20 2016 *)
PROG
(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
(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
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved