hpd at hpdale.org (Harvey P. Dale) writes: > > 1/6 (2^x+4 (1/2-(I Sqrt[3])/2)^x+4 (1/2+(I Sqrt[3])/2)^x) Could also give the periodic part explicitly if desired. Something like 1/3*(2^n + [2,-2,-4,-2,2,4]), letting [] mean the respective value according as n==0to5 mod 6 (in absense of knowing better notation for that :).