Minimal span of set of n elements with no 4-term arithmetic progression.

Terms

a(0) =4a(1) =5a(2) =7a(3) =8a(4) =9a(5) =12a(6) =14a(7) =16a(8) =18a(9) =20a(10) =22a(11) =24a(12) =26a(13) =27a(14) =29a(15) =32a(16) =33a(17) =36a(18) =39a(19) =42a(20) =44a(21) =47a(22) =49a(23) =52a(24) =53a(25) =57a(26) =59a(27) =63a(28) =65a(29) =67