Numbers k such that k*(k+2) gives the concatenation of a number m with itself.

Terms

a(0) =9a(1) =99a(2) =427a(3) =572a(4) =726a(5) =845a(6) =999a(7) =7809a(8) =9999a(9) =36364a(10) =63635a(11) =99999a(12) =326733a(13) =673266a(14) =999999a(15) =4545453a(16) =5454546a(17) =9999999a(18) =47058822a(19) =52941177a(20) =99999999a(21) =331983806a(22) =332667333a(23) =384615385a(24) =422892897a(25) =475524476a(26) =524475523a(27) =577107102a(28) =615384614a(29) =667332666