A033679 a(1) = 2; a(n) is smallest number >= a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.

2, 3, 3, 3, 3, 21, 53, 69, 81, 139, 143, 223, 233, 261, 261, 399, 553, 609, 659, 673, 1017, 1187, 1357, 1571, 1641, 1839, 2151, 2191, 2499, 2511, 2607, 2667, 2681, 3081, 3351, 4291, 4319, 4353, 4489, 4733, 4819, 6003, 6011, 6631, 6797, 7113, 7429, 7547, 7651

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..300

Crossrefs

Cf. A069603, A074338, A033680, A033681, A046254, A046255, A046256, A046257, A046258, A046259, A111524.

Programs

Maple

R:= 2,3: p:= 23: x:= 3:
for count from 3 to 100 do
  for y from x by 2 do
    if isprime(10^(1+ilog10(y))*p+y) then
      R:= R, y; p:= 10^(1+ilog10(y))*p+y; x:= y;
      break
    fi
od od:
R; # Robert Israel, Nov 22 2020

Mathematica

a[1] = 2; 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 ++ ]; k]; Table[ a[n], {n, 47}] (* Robert G. Wilson v, Aug 05 2005 *)

Extensions

More terms from Patrick De Geest, May 15 1998

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