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A248960 Number of ternary words of length n in which all digits 0..2 occur in every 5 consecutive digits. 2
1, 3, 9, 27, 81, 150, 366, 870, 2022, 4686, 10974, 25614, 59742, 139398, 325350, 759198, 1771590, 4134126, 9647262, 22512342, 52533750, 122590422, 286071414, 667563054, 1557794622, 3635198310, 8482932318, 19795382454, 46193598486, 107795266974, 251546100558, 586996465758, 1369788083022 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

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

FORMULA

G.f.: (1+2*x+4*x^2+10*x^3+28*x^4-8*x^5-14*x^6-6*x^8+3*x^10) / ((1+x)*(1-2*x-2*x^3+x^5)). - Colin Barker, Oct 27 2016

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

a(n) = A242317(n-4) * 6.

MATHEMATICA

Join[{1, 3, 9, 27, 81}, LinearRecurrence[{1, 2, 2, 2, -1, -1}, {150, 366, 870, 2022, 4686, 10974}, 30]] (* Harvey P. Dale, Apr 04 2015 *)

PROG

(PARI) Vec((1+2*x+4*x^2+10*x^3+28*x^4-8*x^5-14*x^6-6*x^8+3*x^10)/((1+x)*(1-2*x-2*x^3+x^5)) + O(x^30)) \\ Colin Barker, Oct 27 2016

CROSSREFS

Cf. A242317, A249019.

Sequence in context: A014950 A271351 A036143 * A006521 A289257 A014953

Adjacent sequences:  A248957 A248958 A248959 * A248961 A248962 A248963

KEYWORD

nonn,easy

AUTHOR

Andrew Woods, Jan 12 2015

EXTENSIONS

Changed offset to 0. - N. J. A. Sloane, Jan 15 2015

STATUS

approved

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Last modified April 20 16:17 EDT 2019. Contains 322310 sequences. (Running on oeis4.)