Sum of gcd(x, y) for 1 <= x, y <= n.

Terms

a(0) =1a(1) =5a(2) =12a(3) =24a(4) =37a(5) =61a(6) =80a(7) =112a(8) =145a(9) =189a(10) =220a(11) =288a(12) =325a(13) =389a(14) =464a(15) =544a(16) =593a(17) =701a(18) =756a(19) =880a(20) =989a(21) =1093a(22) =1160a(23) =1336a(24) =1441a(25) =1565a(26) =1700a(27) =1880a(28) =1965a(29) =2205