A056274 - OEIS

%I #6 Aug 22 2017 20:53:07

%S 1,1,4,12,40,116,364,1080,3276,9800,29524,88440,265720,796796,2391440,

%T 7173360,21523360,64566684,193710244,581120880,1743391832,5230147076,

%U 15690529804,47071499760,141214768200

%N Number of primitive (aperiodic) word structures of length n using a 3-ary alphabet.

%C Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same structure.

%D M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

%F Sum mu(d)*A007051(n/d-1) where d|n and n>0.

%Y Cf. A054718.

%K nonn

%O 1,3

%A _Marks R. Nester_