A069605 - OEIS

%I #13 Dec 15 2017 17:35:51

%S 3,1,1,9,3,17,1,3,9,39,33,53,1,21,27,113,99,123,3,91,39,29,141,87,67,

%T 297,87,333,59,67,509,103,279,99,141,107,9,1,123,83,529,521,517,137,

%U 249,459,543,583,513,21,53,1029,657,219,313,17,237,19,689,339,307,23

%N a(1) = 3; a(n) = smallest number such that the concatenation a(1)a(2)...a(n) is a prime.

%e a(6) = 17 and the number 3119317 is a prime.

%t a[1] = 3; a[n_] := a[n] = Block[{k = 1, c = IntegerDigits @ Table[ a[i], {i, n - 1}]}, While[ !PrimeQ[ FromDigits @ Flatten @ Append[c, IntegerDigits[k]]], k += 2]; k]; Table[ a[n], {n, 63}] (* _Robert G. Wilson v_, Aug 05 2005 *)

%Y Cf. A033681, A074339, A092528, A069603, A069605, A069606, A069607, A069608, A069609, A069610, A069611, A111525.

%K nonn,base

%O 1,1

%A _Amarnath Murthy_, Mar 26 2002

%E More terms from _Jason Earls_, Jun 13 2002