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 A108620 2*a(n) = A108618(n) + 3*A108619(n). 3

%I

%S 2,4,4,2,0,-3,-6,-4,2,6,6,2,-5,-10,-6,4,10,8,0,-9,-12,-4,11,20,12,-6,

%T -16,-10,6,19,17,1,-16,-18,-2,16,21,9,-12,-22,-10,12,25,17,-5,-22,-18,

%U 4,22,20,0,-21,-24,-4,23,32,12,-21,-36,-16,23,44,24,-18,-40,-22,18,43,29,-11,-40,-30,10,40,32,-6,-39,-35,3,40,40,2,-36

%N 2*a(n) = A108618(n) + 3*A108619(n).

%H C. Dement, <a href="/A108620/b108620.txt">Table of n, a(n) for n = 0..10000</a>

%H Rémy Sigrist, <a href="/A108620/a108620.png">Colored scatterplot of a(n) for n = 0..10000</a> (where the color is function of n mod 6)

%t a[0] = b[0] = 1;

%t f[n_] := Sign[n]*Mod[n, 2];

%t a[n_] := a[n] = (1/2)*(a[n-1] - 3*b[n-1]) + 3*f[(1/2)*(a[n-1] + b[n-1])] + f[(1/2)*(a[n-1] - 3*b[n-1])] + 1;

%t b[n_] := b[n] = (1/2)*(a[n-1] + b[n-1]) + 1;

%t A108620 = Table[(a[n] + 3*b[n])/2, {n, 0, 100}] (* _Jean-François Alcover_, Feb 25 2015, after _Benoit Jubin_ *)

%o Floretion Algebra Multiplication Program, FAMP Code: 1vessum(*)seq[ + .5'i + .5'j + .5'k + .5e]

%Y Cf. A108618, A108619.

%K easy,sign,look

%O 0,1

%A _Creighton Dement_, Jun 22 2005

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Last modified April 19 03:45 EDT 2021. Contains 343105 sequences. (Running on oeis4.)