A069606 a(1) = 4; a(n) = smallest number such that the juxtaposition a(1)a(2)...a(n) is a prime.

4, 1, 9, 11, 19, 3, 3, 41, 51, 51, 87, 19, 63, 23, 13, 29, 3, 219, 183, 27, 27, 3, 3, 27, 217, 129, 381, 59, 163, 281, 169, 57, 77, 31, 9, 9, 243, 147, 21, 239, 39, 219, 693, 37, 143, 789, 9, 163, 219, 497, 51, 301, 149, 103, 117, 309, 591, 159, 741, 131, 541, 1377, 207

Offset

1,1

Links

Table of n, a(n) for n=1..63.

Example

a(5) = 19 and the number 4191119 is a prime.

Mathematica

a[1] = 4; 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 *)
nxt[{jxt_, a_}]:=Module[{n=1}, While[CompositeQ[jxt*10^IntegerLength[n]+n], n++]; {jxt*10^IntegerLength[ n]+n, n}]; NestList[nxt, {4, 4}, 70][[;; , 2]] (* Harvey P. Dale, Oct 06 2023 *)

Crossrefs

Cf. A069602, A069604, A046254, A074340, A092528, A069603, A069605, A069606, A069607, A069608, A069609, A069610, A069611, A111525.

Sequence in context: A179193 A158199 A091885 * A344109 A193580 A244761

Adjacent sequences: A069603 A069604 A069605 * A069607 A069608 A069609

Keyword

nonn,base

Author

Amarnath Murthy, Mar 26 2002

Extensions

More terms from Jason Earls, Jun 13 2002

Status

approved