A069605 a(1) = 3; a(n) = smallest number such that the concatenation a(1)a(2)...a(n) is a prime.

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, 297, 87, 333, 59, 67, 509, 103, 279, 99, 141, 107, 9, 1, 123, 83, 529, 521, 517, 137, 249, 459, 543, 583, 513, 21, 53, 1029, 657, 219, 313, 17, 237, 19, 689, 339, 307, 23

Offset: 1

Author

Amarnath Murthy, Mar 26 2002

Keywords

• nonn
• base

Examples

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

Crossrefs

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

Programs

Mathematica

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 *)

Extensions

More terms from Jason Earls, Jun 13 2002