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A275778 Tribonacci-like sequence a(n) = a(n-1) + a(n-2) + a(n-3) for n >= 3, with a(0) = 1, a(1) = 2, a(2) = 1. 2
1, 2, 1, 4, 7, 12, 23, 42, 77, 142, 261, 480, 883, 1624, 2987, 5494, 10105, 18586, 34185, 62876, 115647, 212708, 391231, 719586, 1323525, 2434342, 4477453, 8235320, 15147115, 27859888, 51242323, 94249326, 173351537, 318843186, 586444049 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
G.f.: (2 x^2-x-1)/(x^3+x^2+x-1).
a(n) = A276658(n) + A000073(n).
MATHEMATICA
CoefficientList[Series[(-1 - x + 2 x^2)/(-1 + x + x^2 + x^3), {x, 0, 35}], x]
RecurrenceTable[{a[n] == a[n - 1] + a[n - 2] + a[n - 3], a[1] == 1, a[2] == 2, a[3] == 1}, a, {n, 35}]
LinearRecurrence[{1, 1, 1}, {1, 2, 1}, 35]
PROG
(PARI) a(n)=([0, 1, 0; 0, 0, 1; 1, 1, 1]^n*[1; 2; 1])[1, 1] \\ Charles R Greathouse IV, Sep 10 2016
CROSSREFS
Sequence in context: A139769 A357470 A326894 * A007839 A364658 A184345
KEYWORD
nonn,easy
AUTHOR
Nicolas Bègue, Sep 10 2016
STATUS
approved

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Last modified April 13 23:25 EDT 2024. Contains 371652 sequences. (Running on oeis4.)