a(1) = 1, a(2) = 2; for n >= 2, a(n+1) = a(n) + Sum_{i = 1..n} (a(i) - a(1)).

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =14a(5) =35a(6) =90a(7) =234a(8) =611a(9) =1598a(10) =4182a(11) =10947a(12) =28658a(13) =75026a(14) =196419a(15) =514230a(16) =1346270a(17) =3524579a(18) =9227466a(19) =24157818a(20) =63245987a(21) =165580142a(22) =433494438a(23) =1134903171a(24) =2971215074a(25) =7778742050a(26) =20365011075a(27) =53316291174a(28) =139583862446a(29) =365435296163