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A218130
Number of length 6 primitive (=aperiodic or period 6) n-ary words.
3
0, 0, 54, 696, 4020, 15480, 46410, 117264, 261576, 530640, 998910, 1770120, 2984124, 4824456, 7526610, 11387040, 16772880, 24132384, 34006086, 47038680, 63991620, 85756440, 113368794, 148023216, 191088600, 244124400, 308897550, 387400104, 481867596, 594798120
OFFSET
0,3
LINKS
FORMULA
G.f.: -6*x^2*(9+53*x+47*x^2+11*x^3)/(x-1)^7.
a(n) = n^6-n^3-n^2+n.
MAPLE
a:= n-> (((n^3-1)*n-1)*n+1)*n:
seq(a(n), n=0..30);
MATHEMATICA
Table[n^6-n^3-n^2+n, {n, 0, 30}] (* or *) LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {0, 0, 54, 696, 4020, 15480, 46410}, 30] (* Harvey P. Dale, Oct 13 2017 *)
CROSSREFS
Row n=6 of A143324.
Sequence in context: A193152 A253006 A128961 * A321635 A090835 A069980
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Oct 21 2012
STATUS
approved