Numbers k such that k*(k+5) gives the concatenation of two numbers m and m-4.

Terms

a(0) =7a(1) =97a(2) =766a(3) =857a(4) =909a(5) =997a(6) =3284a(7) =6712a(8) =9997a(9) =45451a(10) =54545a(11) =99997a(12) =990099a(13) =999997a(14) =8181818a(15) =9999997a(16) =70588232a(17) =99999997a(18) =343130553a(19) =362637362a(20) =363636360a(21) =420053630a(22) =421052631a(23) =497975708a(24) =502024288a(25) =578947365a(26) =579946366