n times n+4 gives the concatenation of two numbers m and m+5.

Terms

a(0) =463a(1) =534a(2) =716a(3) =820a(4) =3426a(5) =6571a(6) =90905a(7) =980200a(8) =3636359a(9) =6363638a(10) =41176466a(11) =58823531a(12) =413533836a(13) =426573428a(14) =428571424a(15) =432620007a(16) =567379990a(17) =571428573a(18) =573426569a(19) =586466161a(20) =686261109a(21) =725274727a(22) =727272723a(23) =731321306