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A287185 a(n) = 3*a(n-2) + a(n-3) + a(n-5) - 3*a(n-6) - a(n-7), where a(0) = 2, a(1) = 4, a(2) = 7, a(3) = 14, a(4) = 25, a(5) = 47, a(6) = 88, a(7) = 166. 4
2, 4, 7, 14, 25, 47, 88, 166, 311, 586, 1097, 2068, 3877, 7301, 13699, 25778, 48397, 91033, 170969, 321496, 603938, 1135456, 2133310, 4010306, 7535386, 14164226, 26616463, 50028064, 94013615, 176700655, 332068907, 624115579, 1172907376, 2204415644 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Conjecture:  a(n) is the number of letters (0s and 1s) in the n-th iteration of the mapping 00->0010, 1->00, starting with 00; see A288106.

LINKS

Clark Kimberling, Table of n, a(n) for n = 0..2000

Index entries for linear recurrences with constant coefficients, signature (0, 3, 1, 0, 1, 0, -3, -1).

FORMULA

a(n) = 3*a(n-2) + a(n-3) + a(n-5) - 3*a(n-6) - a(n-7), where a(0) = 2, a(1) = 4, a(2) = 7, a(3) = 14, a(4) = 25, a(5) = 47, a(6) = 88, a(7) = 166.

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

MATHEMATICA

LinearRecurrence[{0, 3, 1, 0, 1, 0, -3, -1}, {2, 4, 7, 14, 25, 47, 88, 166}, 40]

CROSSREFS

Cf. A288106.

Sequence in context: A217730 A218576 A054169 * A065491 A072810 A167606

Adjacent sequences:  A287182 A287183 A287184 * A287186 A287187 A287188

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Jun 06 2017

STATUS

approved

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Last modified October 23 12:53 EDT 2019. Contains 328345 sequences. (Running on oeis4.)