First differences of A003591.

Terms

a(0) =1a(1) =2a(2) =3a(3) =1a(4) =6a(5) =2a(6) =12a(7) =4a(8) =17a(9) =7a(10) =8a(11) =34a(12) =14a(13) =16a(14) =68a(15) =28a(16) =32a(17) =87a(18) =49a(19) =56a(20) =64a(21) =174a(22) =98a(23) =112a(24) =128a(25) =348a(26) =196a(27) =224a(28) =256a(29) =353