A033681 a(1) = 3; a(n) is smallest number >= a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.

3, 7, 9, 51, 51, 51, 97, 131, 157, 159, 243, 309, 327, 363, 383, 411, 487, 639, 873, 983, 1231, 1257, 1337, 1549, 1589, 2101, 2159, 2317, 2871, 2907, 4053, 4097, 4597, 4703, 5559, 5799, 6337, 6527, 6561, 6939, 7147, 7167, 7839, 8403, 8873, 9237, 9541, 9771

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Crossrefs

Cf. A069605, A074339, A033680, A033679, A046254, A046255, A046256, A046257, A046258, A046259, A111524.

Programs

Mathematica

a[1] = 3; a[n_] := a[n] = Block[{k = a[n - 1], c = IntegerDigits @ Table[ a[i], {i, n - 1}]}, While[ !PrimeQ[ FromDigits @ Flatten @ Append[c, IntegerDigits[k]]], k += 2]; k]; Table[ a[n], {n, 48}] (* Robert G. Wilson v *)

Extensions

More terms from Patrick De Geest, May 15 1998

More terms from Robert G. Wilson v, Aug 05 2005