a(n) is the smallest positive integer such that n*a(n) contains the string n+a(n) in reverse as a substring. If no such number exists then a(n) = -1.

A339403

a(n) is the smallest positive integer such that n*a(n) contains the string n+a(n) in reverse as a substring. If no such number exists then a(n) = -1.

Terms

    a(0) =0a(1) =-1a(2) =2a(3) =24a(4) =37a(5) =26a(6) =34a(7) =35a(8) =57a(9) =9a(10) =-1a(11) =12a(12) =11a(13) =45a(14) =193a(15) =228a(16) =28a(17) =51a(18) =23a(19) =44a(20) =841a(21) =11a(22) =27a(23) =18a(24) =3a(25) =626a(26) =5a(27) =22a(28) =16a(29) =46716

External references