Left-hand half of triangle A297191.

Terms

a(0) =1a(1) =1a(2) =3a(3) =1a(4) =7a(5) =13a(6) =1a(7) =11a(8) =41a(9) =63a(10) =1a(11) =15a(12) =85a(13) =231a(14) =321a(15) =1a(16) =19a(17) =145a(18) =575a(19) =1289a(20) =1683a(21) =1a(22) =23a(23) =221a(24) =1159a(25) =3649a(26) =7183a(27) =8989a(28) =1a(29) =27