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A130508 a(1)=2. a(2)=3. a(3)=1. a(n+3) = 3 + a(n), for all positive integers n. 2
2, 3, 1, 5, 6, 4, 8, 9, 7, 11, 12, 10, 14, 15, 13, 17, 18, 16, 20, 21, 19, 23, 24, 22, 26, 27, 25, 29, 30, 28, 32, 33, 31, 35, 36, 34, 38, 39, 37, 41, 42, 40, 44, 45, 43, 47, 48, 46, 50, 51, 49, 53, 54, 52, 56, 57, 55, 59, 60, 58, 62, 63, 61, 65, 66, 64, 68 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
This sequence is a permutation of the positive integers, where each a(n) is the smallest positive integer not occurring earlier in the sequence such that the m-th term of the inverse permutation A130509 never equals a(m), for all positive integers m.
LINKS
FORMULA
a(1)=2, a(2)=3, a(3)=1, a(4)=5, a(n)=a(n-1)+a(n-3)-a(n-4). - Harvey P. Dale, Feb 02 2015
a(n) = n - 2*cos(2*n*Pi/3). - Wesley Ivan Hurt, Sep 27 2017
G.f.: x*(2+x-2*x^2+2*x^3) / ( (1+x+x^2)*(x-1)^2 ). - R. J. Mathar, Oct 03 2021
Sum_{n>=1} (-1)^(n+1)/a(n) = 2*Pi/(3*sqrt(3)) - log(2)/3. - Amiram Eldar, Jan 31 2023
MATHEMATICA
Transpose[NestList[{#[[2]], #[[3]], #[[1]]+3}&, {2, 3, 1}, 100]][[1]] (* Harvey P. Dale, Sep 08 2011 *)
LinearRecurrence[{1, 0, 1, -1}, {2, 3, 1, 5}, 100] (* Harvey P. Dale, Feb 02 2015 *)
CROSSREFS
Cf. A130509.
Sequence in context: A195508 A049274 A339470 * A341635 A182938 A329445
KEYWORD
easy,nonn
AUTHOR
Leroy Quet, Jun 01 2007
STATUS
approved

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)