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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.
12
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
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 *)
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Sep 23 2002
EXTENSIONS
Corrected and extended by Robert G. Wilson v, Aug 05 2005
STATUS
approved