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A212979 Number of (w,x,y) with all terms in {0,...,n} and range=average. 2
1, 1, 1, 7, 10, 13, 19, 25, 34, 40, 49, 61, 70, 82, 94, 109, 124, 136, 154, 172, 190, 208, 226, 250, 271, 292, 316, 340, 367, 391, 418, 448, 475, 505, 535, 568, 601, 631, 667, 703, 739, 775, 811, 853, 892, 931, 973, 1015, 1060, 1102, 1147, 1195, 1240 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

For a guide to related sequences, see A212959.

LINKS

Table of n, a(n) for n=0..52.

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

FORMULA

a(n) = 2*a(n-1)-2*a(n-2)+2*a(n-3)-a(n-4)+a(n-5)-2*a(n-6)+2*a(n-7)-2*a(n-8)+a(n-9).

G.f.: (1 - x + x^2 + 5*x^3 - 3*x^4 + 5*x^5 + x^6 - x^7 + x^8 )/(1 - 2*x + 2*x^2 - 2*x^3 + x^4 - x^5 + 2*x^6 - 2*x^7 + 2*x^8 - x^9).

EXAMPLE

a(3)=7 counts these (w,x,y):

(0,0,0) and the six permutations of (1,2,3).

MATHEMATICA

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

(Do[If[Max[w, x, y] - Min[w, x, y] == (w + x + y)/3, s = s + 1],

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

m = Map[t[#] &, Range[0, 60]]   (* A212979 *)

CROSSREFS

Cf. A212959.

Sequence in context: A120153 A226969 A007770 * A114961 A219045 A199427

Adjacent sequences:  A212976 A212977 A212978 * A212980 A212981 A212982

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jun 03 2012

STATUS

approved

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Last modified April 15 07:59 EDT 2021. Contains 342975 sequences. (Running on oeis4.)