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A249019 Number of ternary words of length n in which all digits 0..2 occur in every 6 consecutive digits. 2
1, 3, 9, 27, 81, 243, 540, 1440, 3804, 9960, 25908, 67344, 175884, 458832, 1196364, 3119304, 8134164, 21212832, 55316892, 144249168, 376159644, 980918904, 2557958964, 6670420704, 17394543180, 45359994336, 118285895244, 308455762488, 804364332180, 2097551985168, 5469815336796, 14263713072192 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
a(n) = a(n-1) + 2*a(n-2) + 3*a(n-3) + 5*a(n-4) + 6*a(n-5) - a(n-6) - a(n-7) - a(n-9) - a(n-10), for n>=16.
G.f.: (1 + 2*x + 4*x^2 + 9*x^3 + 22*x^4 + 60*x^5 - 8*x^6 - 14*x^7 - 8*x^9 - 26*x^10 + 3*x^12 + 3*x^15)/(1 - x - 2*x^2 - 3*x^3 - 5* x^4 - 6*x^5 + x^6 + x^7 + x^9 + x^10 - Colin Barker, Jan 12 2015
MATHEMATICA
LinearRecurrence[{1, 2, 3, 5, 6, -1, -1, 0, -1, -1}, {1, 3, 9, 27, 81, 243, 540, 1440, 3804, 9960, 25908, 67344, 175884, 458832, 1196364, 3119304}, 40] (* Harvey P. Dale, Feb 05 2019 *)
PROG
(PARI) Vec(-12*x^6*(20*x^9 +27*x^8 +9*x^7 +23*x^6 +28*x^5 -110*x^4 -138*x^3 -107*x^2 -75*x -45) / (x^10 +x^9 +x^7 +x^6 -6*x^5 -5*x^4 -3*x^3 -2*x^2 -x +1) + O(x^100)) \\ Colin Barker, Jan 12 2015
CROSSREFS
Sequence in context: A291007 A038002 A272338 * A216096 A300148 A190128
KEYWORD
nonn,easy
AUTHOR
Andrew Woods, Jan 12 2015
STATUS
approved

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Last modified July 12 09:44 EDT 2024. Contains 374239 sequences. (Running on oeis4.)