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A130766 3n+2 sandwiched by tripled 3n+1 . 1
1, 1, 1, 2, 4, 4, 4, 5, 7, 7, 7, 8, 10, 10, 10, 11, 13, 13, 13, 14, 16, 16, 16, 17, 19, 19, 19, 20, 22, 22, 22, 23, 25, 25, 25, 26, 28, 28, 28, 29, 31, 31, 31, 32, 34, 34, 34, 35, 37, 37, 37, 38, 40, 40, 40, 41, 43, 43, 43, 44, 46, 46, 46, 47, 49, 49, 49, 50, 52, 52, 52, 53, 55 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,4
LINKS
FORMULA
From Chai Wah Wu, Jun 17 2016: (Start)
a(n) = a(n-1) + a(n-4) - a(n-5) for n > 4.
G.f.: (x^4 + x^3 + 1)/(x^5 - x^4 - x + 1). (End)
a(n) = 2*floor(n/4) + floor((n+1)/4) + 1. - Ridouane Oudra, Jan 26 2024
Sum_{n>=0} (-1)^n/a(n) = Pi/(3*sqrt(3)) (A073010). - Amiram Eldar, Feb 11 2024
MATHEMATICA
CoefficientList[Series[(x^4 + x^3 + 1) / (x^5 - x^4 - x + 1), {x, 0, 100}], x] (* Vincenzo Librandi, Jun 18 2016 *)
LinearRecurrence[{1, 0, 0, 1, -1}, {1, 1, 1, 2, 4}, 100] (* Harvey P. Dale, Apr 18 2023 *)
PROG
(Magma) I:=[1, 1, 1, 2, 4]; [n le 5 select I[n] else Self(n-1)+Self(n-4)-Self(n-5): n in [1..80]]; // Vincenzo Librandi, Jun 18 2016
CROSSREFS
Cf. A073010.
Sequence in context: A178976 A352426 A372323 * A227190 A284581 A284560
KEYWORD
nonn
AUTHOR
Paul Curtz, Aug 18 2007
STATUS
approved

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Last modified July 21 18:08 EDT 2024. Contains 374475 sequences. (Running on oeis4.)