A121511 a(n) = a(n-1) + a(n-4) - a(n-5).

1, 5, 13, 25, 5, 9, 17, 29, 9, 13, 21, 33, 13, 17, 25, 37, 17, 21, 29, 41, 21, 25, 33, 45, 25, 29, 37, 49, 29, 33, 41, 53, 33, 37, 45, 57, 37, 41, 49, 61, 41, 45, 53, 65, 45, 49, 57, 69, 49, 53, 61, 73, 53, 57, 65, 77, 57, 61, 69, 81, 61, 65, 73, 85, 65, 69, 77

Offset: 1

Author

Roger L. Bagula, Sep 07 2006

Keywords

• nonn
• easy

Comments

This sequence gives a linearly increasing triangle shaped form on plotting.

Links

• Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).

Crossrefs

Cf. A001844.

Programs

Mathematica

LinearRecurrence[{1,0,0,1,-1},{1,5,13,25,5},67] (* James C. McMahon, Oct 19 2024 *)

PARI

Vec(-x*(-1-4*x-8*x^2-12*x^3+21*x^4)/((1+x)*(x^2+1)*(x-1)^2) + O(x^75)) \\ Jinyuan Wang, Jun 07 2020

Formula

G.f.: -x*(-1-4*x-8*x^2-12*x^3+21*x^4)/((1+x)*(x^2+1)*(x-1)^2).

a(n) = n + 17/2 + 7*(-1)^n/2 + A057077(n+1)*A010720(n-1).

Extensions

Definition replaced by recurrence - The Assoc. Editors of the OEIS, Oct 14 2009

More terms from Jinyuan Wang, Jun 07 2020