OFFSET
0,4
COMMENTS
k>=0, a(7+2*k)=7, (for odd indices >=7),
also k>=0, a(14+2*k)=15+k, (for even indices >=14).
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
FORMULA
From Chai Wah Wu, Oct 12 2018: (Start)
a(n) = 2*a(n-2) - a(n-4) for n > 16.
G.f.: x*(-14*x^15 + 16*x^13 - 7*x^8 + 9*x^6 - 4*x^5 - 3*x^4 + 2*x^3 + x + 1)/((x - 1)^2*(x + 1)^2). (End)
MATHEMATICA
Table[Mod[n(3n-1)/2, n+2], {n, 0, 200}]
With[{nn=90}, Mod[PolygonalNumber[5, Range[0, nn]], Range[2, nn+2]]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 28 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jul 29 2010
STATUS
approved