OFFSET
0,3
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,1,0,-1,-1,1).
FORMULA
From Henry Bottomley, Sep 05 2000: (Start)
a(n) = floor((n^2 - 2*n + 18)/6) for n>2.
a(n) = a(n-2) + a(n-3) - a(n-5) + 2.
a(n) = A008747(n-2) + 2 for n>2. (End)
MATHEMATICA
CoefficientList[Series[(1+x^8)/((1-x)(1-x^2)(1-x^3)), {x, 0, 50}], x] (* Vincenzo Librandi, Feb 25 2012 *)
Join[{1, 1, 2}, Floor[((Range[3, 50] -1)^2 +17)/6]] (* G. C. Greubel, Aug 04 2019 *)
PROG
(PARI) my(x='x+O('x^50)); Vec((1+x^8)/((1-x)*(1-x^2)*(1-x^3))) \\ G. C. Greubel, Aug 04 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( (1+x^8)/((1-x)*(1-x^2)*(1-x^3)) )); // G. C. Greubel, Aug 04 2019
(Sage) ((1+x^8)/((1-x)*(1-x^2)*(1-x^3))).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Aug 04 2019
(GAP) Concatenation([1, 1, 2], List([3..50], n-> Int(((n-1)^2 +17)/6))); # G. C. Greubel, Aug 04 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved