%I #14 May 26 2022 09:52:00
%S 1,3,3,29,3,3,19,3,3,7,3,3,17,3,3,23,3,3,17,3,3,13,3,3,11,3,3,23,3,3,
%T 7,3,3,89,3,3,29,3,3,11,3,3,52433,3,3,23,3,3,71,3,3,7,3,3
%N a(1) = 1; for n>1, a(n) = the smallest prime divisor of the number C(n) formed from the reverse concatenation of 1,2,3,... up to n.
%e a(4)= 29, 29 is the smallest prime divisor of 4321 =29*149
%t b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[Length[w] - k + 1]]], {k, 1, Length[w]}]; p = FromDigits[Reverse[a]]; AppendTo[b, First[First[FactorInteger[p]]]], {n, 1, 21}]; b (* _Artur Jasinski_, Apr 04 2008 *)
%Y Cf. A075019.
%Y Cf. A104759, A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138960, A138961, A138962.
%K base,nonn
%O 1,2
%A _Amarnath Murthy_, Sep 01 2002
%E More terms from _Sascha Kurz_, Jan 03 2003