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A061800 a(n) = n + (-1)^(n mod 3). 3
1, 0, 3, 4, 3, 6, 7, 6, 9, 10, 9, 12, 13, 12, 15, 16, 15, 18, 19, 18, 21, 22, 21, 24, 25, 24, 27, 28, 27, 30, 31, 30, 33, 34, 33, 36, 37, 36, 39, 40, 39, 42, 43, 42, 45, 46, 45, 48, 49, 48, 51, 52, 51, 54, 55, 54, 57, 58, 57, 60, 61, 60, 63, 64, 63, 66, 67, 66, 69, 70, 69, 72 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

The arithmetic function v_3(n,3) as defined in A289187. - Robert Price, Aug 22 2017

LINKS

Harry J. Smith, Table of n, a(n) for n=0..1000

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

FORMULA

O.g.f.: (1-x+3*x^2)/((-1+x)^2*(1+x+x^2)). - R. J. Mathar, Apr 02 2008

a(n) = (3*n + 1 - 4*cos(2*(n+2)*Pi/3))/3. - Wesley Ivan Hurt, Sep 26 2017

a(n) = a(n-1) + a(n-3) - a(n-4) for n > 3. - Wesley Ivan Hurt, Oct 07 2017

EXAMPLE

a(4) = 4 + (-1)^1 = 3.

MAPLE

A061800:=n->n+(-1)^(n mod 3): seq(A061800(n), n=0..150); # Wesley Ivan Hurt, Oct 07 2017

MATHEMATICA

Table[n + (-1)^Mod[n, 3], {n, 0, 80}] (* Vincenzo Librandi, Aug 23 2017 *)

PROG

(PARI) { for (n=0, 1000, write("b061800.txt", n, " ", n + (-1)^(n%3)) ) } \\ Harry J. Smith, Jul 28 2009

(MAGMA) [n+(-1)^(n mod 3): n in [0..80]]; // Vincenzo Librandi, Aug 23 2017

CROSSREFS

Cf. A004442, A014681, A289187.

Sequence in context: A074372 A049276 A101684 * A218789 A324335 A238162

Adjacent sequences:  A061797 A061798 A061799 * A061801 A061802 A061803

KEYWORD

easy,nonn

AUTHOR

Olivier Gérard, Jun 22 2001

STATUS

approved

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Last modified May 25 04:50 EDT 2019. Contains 323539 sequences. (Running on oeis4.)