OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..200
EXAMPLE
a(7) = 17 and the number 71933317 is a prime.
MATHEMATICA
a[1] = 7; 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, 67}] (* Robert G. Wilson v, Aug 05 2005 *)
nxt[{j_, a_}]:=Module[{k=1}, While[CompositeQ[j*10^IntegerLength[k]+k], k++]; {j*10^IntegerLength[k]+k, k}]; NestList[nxt, {7, 7}, 70][[All, 2]] (* Harvey P. Dale, May 06 2022 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Amarnath Murthy, Mar 26 2002
EXTENSIONS
More terms from Jason Earls, Jun 13 2002
STATUS
approved