OFFSET
0,2
LINKS
Paolo Xausa, Table of n, a(n) for n = 0..10000
Eric Angelini, k-chunks sum and division by k, post to the SeqFan list, Mar 22 2013.
Index entries for linear recurrences with constant coefficients, signature (0,0,2,0,0,-1).
FORMULA
a(n) = 2*a(n-3) - a(n-6).
G.f.: (1 + 2*x + 3*x^2 + 2*x^3 + x^4 + 3*x^5)/((1 - x)*(1 + x + x^2))^2.
a(n) = A222256(n) + 1. - Paolo Xausa, Sep 30 2025
MATHEMATICA
A222257[n_] := (n - 2)*Mod[n, 3]! + 3; (* after Thomas Scheuerle *)
Array[A222257, 100, 0] (* or *)
LinearRecurrence[{0, 0, 2, 0, 0, -1}, {1, 2, 3, 4, 5 , 9}, 100] (* Paolo Xausa, Sep 30 2025 *)
PROG
(PARI) a(n) = (n-2)*(n%3)!+3 \\ Thomas Scheuerle, Sep 25 2025
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric Angelini and M. F. Hasler, Mar 23 2013
STATUS
approved