OFFSET
0,6
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,1,-1).
FORMULA
O.g.f.: x^4/((1-x)*(1-2*x+x^2-x^5)).
a(n) = Sum_{i=1..floor((n+1)/5)} binomial(n+1-3*i,2*i). - Andrew Howroyd, Sep 19 2025
EXAMPLE
a(5) = 3 because we have: {0,0,0,0,0}, {0,0,0,0,1}, {1,0,0,0,0}.
MATHEMATICA
nn=40; a=x^4/(1-x); CoefficientList[Series[(a+1)/((1-a x/(1-x)))*1/(1-x)-1/(1-x), {x, 0, nn}], x]
PROG
(PARI) a(n) = sum(i=1, (n+1)\5, binomial(n+1-3*i, 2*i)) \\ Andrew Howroyd, Sep 19 2025
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Geoffrey Critzer, Jan 12 2013
EXTENSIONS
a(41) onwards from Andrew Howroyd, Sep 19 2025
STATUS
approved