a(n) = Sum_{k=1..n} k*lcm(k,k')/gcd(k,k'), where k' is arithmetic derivative of k.

Terms

a(0) =0a(1) =4a(2) =13a(3) =17a(4) =42a(5) =222a(6) =271a(7) =319a(8) =373a(9) =1073a(10) =1194a(11) =1338a(12) =1507a(13) =3271a(14) =5071a(15) =5103a(16) =5392a(17) =6148a(18) =6509a(19) =7109a(20) =11519a(21) =17811a(22) =18340a(23) =19924a(24) =20174a(25) =30314a(26) =30341a(27) =31909a(28) =32750a(29) =60650