Voozh

A122164

a(0) = 0, a(1) = 1, s = 0; for n >= 2, if a(n-1) is even and s = 0 then set a(n) = a(n-1)/2 and s = 1; otherwise set a(n) = a(n-1) + a(n-2) and s = 0.

0, 1, 1, 2, 1, 3, 4, 2, 6, 3, 9, 12, 6, 18, 9, 27, 36, 18, 54, 27, 81, 108, 54, 162, 81, 243, 324, 162, 486, 243, 729, 972, 486, 1458, 729, 2187, 2916, 1458, 4374, 2187, 6561, 8748, 4374, 13122, 6561, 19683, 26244, 13122, 39366, 19683, 59049, 78732, 39366

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OFFSET

0,4

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

FORMULA

For i >= 1, a(5i) = 3^i, a(5i+1) = 4*3^(i-1), a(5i+2) = 2*3^(i-1), a(5i+3) = 2*3^i, a(5i+4) = 3^i. - N. J. A. Sloane, Aug 06 2008

O.g.f.: x(-1-x-2x^2-x^3-3x^4-x^5+x^6)/(3x^5-1). - R. J. Mathar, Aug 07 2008

MATHEMATICA

Do[a[n] = {0, 1, 1, 2, 1, 3, 4, 2}[[n+1]], {n, 0, 7}]; a[n_] := a[n] = 3*a[n-5]; Array[a, 53, 0] (* Jean-François Alcover, Nov 07 2016 *)

nxt[{s_, a_, b_}]:=If[EvenQ[b]&&s==0, {1, b, b/2}, {0, b, a+b}]; NestList[nxt, {0, 0, 1}, 60][[All, 2]] (* Harvey P. Dale, Oct 25 2020 *)

CROSSREFS