Knuth's sequence (or Knuth numbers): a(n+1) = 1 + min( 2*a(floor(n/2)), 3*a(floor(n/3)) ).

Terms

a(0) =1a(1) =3a(2) =3a(3) =4a(4) =7a(5) =7a(6) =7a(7) =9a(8) =9a(9) =10a(10) =13a(11) =13a(12) =13a(13) =15a(14) =15a(15) =19a(16) =19a(17) =19a(18) =19a(19) =21a(20) =21a(21) =22a(22) =27a(23) =27a(24) =27a(25) =27a(26) =27a(27) =28a(28) =31a(29) =31