a(n+1) = 1 + Sum_{k=1..n} a(gcd(n,k)).

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =12a(5) =17a(6) =28a(7) =35a(8) =51a(9) =66a(10) =91a(11) =102a(12) =150a(13) =163a(14) =210a(15) =259a(16) =325a(17) =342a(18) =454a(19) =473a(20) =608a(21) =701a(22) =823a(23) =846a(24) =1099a(25) =1168a(26) =1355a(27) =1500a(28) =1786a(29) =1815