a(1) = 1; for n > 1, a(n) = the smallest prime divisor of the number C(n) formed from the concatenation of 1,2,3,... up to n.
A075019
a(1) = 1; for n > 1, a(n) = the smallest prime divisor of the number C(n) formed from the concatenation of 1,2,3,... up to n.
Terms
- a(0) =1a(1) =2a(2) =3a(3) =2a(4) =3a(5) =2a(6) =127a(7) =2a(8) =3a(9) =2a(10) =3a(11) =2a(12) =113a(13) =2a(14) =3a(15) =2a(16) =3a(17) =2a(18) =13a(19) =2a(20) =3a(21) =2a(22) =3a(23) =2a(24) =5a(25) =2a(26) =3a(27) =2a(28) =3a(29) =2
External references
- oeis: A075019