Digits of composite k start as k', where k' is the arithmetic derivative of k.

Terms

a(0) =1243a(1) =40633a(2) =43489a(3) =132217a(4) =132653a(5) =163817a(6) =355247a(7) =356071a(8) =356483a(9) =356689a(10) =1020403a(11) =1021211a(12) =1023433a(13) =1024039a(14) =1024241a(15) =1025251a(16) =1026059a(17) =1026463a(18) =1027069a(19) =1027877a(20) =1028281a(21) =1029493a(22) =4018657a(23) =4086233a(24) =4120399a(25) =4236923a(26) =4324963a(27) =4348051a(28) =4386749a(29) =4468027