Number of 4-ary sequences with primitive period n.

Terms

a(0) =1a(1) =4a(2) =12a(3) =60a(4) =240a(5) =1020a(6) =4020a(7) =16380a(8) =65280a(9) =262080a(10) =1047540a(11) =4194300a(12) =16772880a(13) =67108860a(14) =268419060a(15) =1073740740a(16) =4294901760a(17) =17179869180a(18) =68719210560a(19) =274877906940