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A212985
Number of (w,x,y) with all terms in {0,...,n} and 3w = 3x + y.
2
1, 2, 3, 7, 9, 11, 18, 21, 24, 34, 38, 42, 55, 60, 65, 81, 87, 93, 112, 119, 126, 148, 156, 164, 189, 198, 207, 235, 245, 255, 286, 297, 308, 342, 354, 366, 403, 416, 429, 469, 483, 497, 540, 555, 570, 616, 632, 648, 697, 714, 731, 783, 801, 819, 874
OFFSET
0,2
COMMENTS
For a guide to related sequences, see A212959.
FORMULA
a(n) = a(n-1) + 2*a(n-3) - 2*a(n-4) - a(n-6) + a(n-7).
G.f.: f(x)/g(x), where f(x) = 1 + x + x^2 + 2*x^3 and g(x) = ((1+x+x^2)^2)*((1-x)^3).
MATHEMATICA
t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[3 w == 3 x + y, s = s + 1],
{w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];
m = Map[t[#] &, Range[0, 70]] (* A212985 *)
CROSSREFS
Cf. A212959.
Sequence in context: A345745 A280110 A203234 * A103797 A262814 A328982
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 04 2012
STATUS
approved