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 A108620 2*a(n) = A108618(n) + 3*A108619(n). 3
 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, -16, -10, 6, 19, 17, 1, -16, -18, -2, 16, 21, 9, -12, -22, -10, 12, 25, 17, -5, -22, -18, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS C. Dement, Table of n, a(n) for n = 0..10000 MATHEMATICA a[0] = b[0] = 1; f[n_] := Sign[n]*Mod[n, 2]; 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; b[n_] := b[n] = (1/2)*(a[n-1] + b[n-1]) + 1; A108620 = Table[(a[n] + 3*b[n])/2, {n, 0, 100}] (* Jean-François Alcover, Feb 25 2015, after Benoit Jubin *) PROG Floretion Algebra Multiplication Program, FAMP Code: 1vessum(*)seq[ + .5'i + .5'j + .5'k + .5e] CROSSREFS Cf. A108618, A108619. Sequence in context: A079536 A058923 A107500 * A070512 A156346 A156283 Adjacent sequences:  A108617 A108618 A108619 * A108621 A108622 A108623 KEYWORD easy,sign,look AUTHOR Creighton Dement, Jun 22 2005 STATUS approved

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