OFFSET
0,3
COMMENTS
This sequence has the form (0+4k,0+4k,2+4k,2+4k,2+4k) for k>=0.
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1).
FORMULA
a(n + 5*k) = a(n) + 4*k.
From Colin Barker, Jul 04 2017: (Start)
G.f.: 2*x^2*(1 + x)*(1 - x + x^2) / ((1 - x)^2*(1 + x + x^2 + x^3 + x^4)).
a(n) = a(n-1) + a(n-5) - a(n-6) for n>5.
(End)
MATHEMATICA
Table[Count[Mod[Table[2(2(n-1)^2+k)-1, {k, 1, 4 n-2}], 5], 0], {n, 0, 50}]
PROG
(PARI) concat(vector(2), Vec(2*x^2*(1 + x)*(1 - x + x^2) / ((1 - x)^2*(1 + x + x^2 + x^3 + x^4)) + O(x^100))) \\ Colin Barker, Jul 04 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ralf Steiner, Jun 28 2017
STATUS
approved