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A101551 a(n) = C(n-2,2)+C(n-5,5)+...+C(n-(3*floor((n-3)/3)+2),3*floor((n-3)/3)+2). 4
0, 0, 0, 0, 1, 3, 6, 10, 15, 21, 29, 42, 66, 111, 192, 330, 554, 906, 1452, 2303, 3651, 5826, 9382, 15225, 24807, 40431, 65748, 106584, 172321, 278184, 448980, 725140, 1172412, 1897380, 3072365, 4975551, 8055918, 13038606, 21096027, 34125561 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,6
LINKS
FORMULA
G.f.: x^4/((1-x)^3-x^6) = -x^4/ ((x^2+x-1)*(x^4-x^3+2*x^2-2*x+1)).
a(n) = Sum_{k=0..n} if(mod(k+1, 3)=0, C(n-k, k), 0).
a(n+2) = Sum_{k=0..floor(n/6)} binomial(n-3k, 3k+2). - Paul Barry, Jan 13 2005
MATHEMATICA
CoefficientList[Series[x^4/((1-x)^3-x^6), {x, 0, 50}], x] (* Vincenzo Librandi, Jul 08 2012 *)
LinearRecurrence[{3, -3, 1, 0, 0, 1}, {0, 0, 0, 0, 1, 3}, 40] (* Harvey P. Dale, Feb 20 2014 *)
CROSSREFS
Sequence in context: A025745 A175724 A335184 * A227430 A051166 A188278
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Dec 06 2004
STATUS
approved

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Last modified June 19 09:20 EDT 2024. Contains 373494 sequences. (Running on oeis4.)