Number of words of weight n in the free central groupoid on one generator.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =6a(5) =8a(6) =26a(7) =55a(8) =148a(9) =377a(10) =1066a(11) =2853a(12) =8044a(13) =22298a(14) =63134a(15) =178399a(16) =509944a(17) =1460728a(18) =4213962a(19) =12194213a(20) =35452092a(21) =103381821a(22) =302507766a(23) =887572293