a(n) = (1/4 + 1/6 + ... + 1/c(n))*LCM{4, 6, ..., c(n)}, where c(n) = n-th composite number.

Terms

a(0) =1a(1) =5a(2) =13a(3) =47a(4) =271a(5) =301a(6) =2287a(7) =2455a(8) =5225a(9) =5505a(10) =5757a(11) =5997a(12) =68487a(13) =70797a(14) =365073a(15) =4884549a(16) =15054047a(17) =15440147a(18) =15800507a(19) =32276689a(20) =32931889a(21) =570652913a(22) =581154833a(23) =591365033a(24) =11419719227a(25) =11598790427a(26) =11773384847a(27) =11939665247a(28) =12098387447a(29) =12253582487