Numbers n = concat(a,b) such that phi(n) = phi(a) * phi(b), where phi = A000010.

Terms

a(0) =78a(1) =780a(2) =897a(3) =918a(4) =1179a(5) =1365a(6) =1776a(7) =2574a(8) =2598a(9) =2967a(10) =3168a(11) =3762a(12) =4758a(13) =5775a(14) =5796a(15) =7800a(16) =7875a(17) =7917a(18) =8217a(19) =8970a(20) =9180a(21) =9576a(22) =11790a(23) =13650a(24) =13662a(25) =13875a(26) =13896a(27) =14391a(28) =17760a(29) =18564