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A212988 Number of (w,x,y) with all terms in {0,...,n} and 4*w = x+y. 2
1, 1, 2, 4, 7, 9, 12, 16, 21, 25, 30, 36, 43, 49, 56, 64, 73, 81, 90, 100, 111, 121, 132, 144, 157, 169, 182, 196, 211, 225, 240, 256, 273, 289, 306, 324, 343, 361, 380, 400, 421, 441, 462, 484, 507, 529, 552, 576, 601, 625, 650, 676, 703, 729, 756, 784 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

For a guide to related sequences, see A212959.

LINKS

Table of n, a(n) for n=0..55.

Index entries for linear recurrences with constant coefficients, signature (2,-1,0,1,-2,1).

FORMULA

a(n) = 2*a(n-1)-a(n-2)+a(n-4)-2*a(n-5)+a(n-6).

G.f.: f(x)/g(x), where f(x) = 1 - x + x^2 + x^3

and g(x) = (1 + x + x^2 + x^3)(1-x)^3.

MATHEMATICA

t = Compile[{{n, _Integer}}, Module[{s = 0},

(Do[If[4 w == x + y, s = s + 1],

{w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];

m = Map[t[#] &, Range[0, 70]]   (* A212988 *)

CROSSREFS

Cf. A212959.

Sequence in context: A024193 A064550 A186357 * A064491 A120878 A137996

Adjacent sequences:  A212985 A212986 A212987 * A212989 A212990 A212991

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jun 04 2012

STATUS

approved

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Last modified August 3 20:08 EDT 2020. Contains 336201 sequences. (Running on oeis4.)