Davenport-Schinzel numbers of degree 4 on n symbols.

Terms

a(0) =1a(1) =4a(2) =8a(3) =12a(4) =17a(5) =22a(6) =27a(7) =32a(8) =37a(9) =42a(10) =47a(11) =53a(12) =58a(13) =64a(14) =69a(15) =75a(16) =81a(17) =86a(18) =92a(19) =98a(20) =104