a(0)=1; a(n) = gcd(a(n-1), n) + lcm(a(n-1), n).

Terms

a(0) =1a(1) =2a(2) =4a(3) =13a(4) =53a(5) =266a(6) =800a(7) =5601a(8) =44809a(9) =403282a(10) =2016412a(11) =22180533a(12) =88722135a(13) =1153387756a(14) =8073714294a(15) =40368571473a(16) =645897143569