A074345 a(1) = 9; a(n) is smallest number > a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.

9, 11, 21, 33, 39, 71, 73, 81, 101, 123, 193, 257, 271, 293, 379, 387, 407, 627, 669, 931, 1073, 1179, 1273, 1481, 2587, 2627, 2923, 3063, 3617, 3931, 4073, 4093, 4199, 4491, 4801, 5387, 5647, 5739, 5859, 5979, 6149, 6369, 7527, 8053, 8207, 8647, 8949, 8981

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..200

Mathematica

a[1] = 9; a[n_] := a[n] = Block[{k = a[n - 1] + 1 + Mod[a[n - 1], 2], 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 *)
nxt[{j_, a_}]:=Module[{c=a+2}, While[CompositeQ[j*10^IntegerLength[c]+c], c+=2]; {j*10^IntegerLength[c]+c, c}]; NestList[nxt, {9, 9}, 50][[All, 2]] (* Harvey P. Dale, Jan 26 2022 *)

Crossrefs

Cf. A046259, A069611, A074336, A074338, A074339, A074340, A074341, A074342, A074343, A074344, A074346.

Sequence in context: A046259 A258452 A299250 * A022323 A106525 A103510

Adjacent sequences: A074342 A074343 A074344 * A074346 A074347 A074348

Keyword

nonn,base

Author

Zak Seidov, Sep 23 2002

Extensions

Corrected and extended by Robert G. Wilson v, Aug 05 2005

Status

approved