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A069607 a(1) = 5; a(n) = smallest number such that the juxtaposition a(1)a(2)...a(n) is a prime.

%I A069607 #18 May 09 2021 09:40:12
%S A069607 5,3,23,1,3,9,21,9,21,23,43,3,23,7,21,89,37,21,137,1,119,493,143,133,
%T A069607 483,267,179,7,333,359,439,101,33,31,533,19,63,39,333,839,63,693,423,
%U A069607 327,73,29,39,21,517,27,99,251,7,411,243,33,149,49,227,283,303,351,303
%N A069607 a(1) = 5; a(n) = smallest number such that the juxtaposition a(1)a(2)...a(n) is a prime.
%H A069607 Michael S. Branicky, <a href="/A069607/b069607.txt">Table of n, a(n) for n = 1..610</a>
%e A069607 a(5) = 3 and the number 532313 is a prime.
%t A069607 a[1] = 5; 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 *)
%o A069607 (Python)
%o A069607 from sympy import isprime
%o A069607 def aupton(terms):
%o A069607   astr, alst = '5', [5]
%o A069607   for n in range(2, terms+1):
%o A069607     an = 1
%o A069607     while not isprime(int(astr + str(an))): an += 1
%o A069607     astr, alst = astr + str(an), alst + [an]
%o A069607   return alst
%o A069607 print(aupton(63)) # _Michael S. Branicky_, May 03 2021
%Y A069607 Cf. A069602, A069604, A046255, A074341, A092528, A069603, A069605, A069606, A069607, A069608, A069609, A069610, A069611, A111525.
%K A069607 nonn,base
%O A069607 1,1
%A A069607 _Amarnath Murthy_, Mar 26 2002
%E A069607 More terms from _Jason Earls_, Jun 13 2002