Number of primitive (aperiodic) word structures of length n which contain exactly four different symbols.

A056280

Number of primitive (aperiodic) word structures of length n which contain exactly four different symbols.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =1a(4) =10a(5) =65a(6) =350a(7) =1700a(8) =7770a(9) =34095a(10) =145750a(11) =611435a(12) =2532530a(13) =10391395a(14) =42355940a(15) =171797200a(16) =694337290a(17) =2798799150a(18) =11259666950a(19) =45232081795a(20) =181509069700a(21) =727778478075

External references