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

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

Offset: 0

Author

Creighton Dement, Jun 22 2005

Keywords

• easy
• sign
• look

Comments

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

Links

• Creighton Dement, Table of n, a(n) for n = 0..10000
• Rémy Sigrist, Colored scatterplot of a(n) for n = 0..10000 (where the color is function of n mod 6)

Crossrefs

Cf. A108618, A108619.

Programs

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 *)