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A074340 a(1) = 5; a(n) is smallest number > a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.

%I A074340 #12 May 09 2021 09:40:19
%S A074340 5,9,23,37,39,47,57,97,119,187,257,271,273,281,309,367,449,529,687,
%T A074340 759,933,1031,1131,1237,1263,1343,1731,1861,2177,2337,2589,2607,2743,
%U A074340 3191,3199,3281,3499,3807,3867,4133,6079,6189,6593,7207,7479,7523,8569,8571
%N A074340 a(1) = 5; a(n) is smallest number > a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.
%H A074340 Michael S. Branicky, <a href="/A074340/b074340.txt">Table of n, a(n) for n = 1..411</a>
%t A074340 a[1] = 5; 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_ *)
%o A074340 (Python)
%o A074340 from sympy import isprime
%o A074340 def aupton(terms):
%o A074340   alst, astr = [5], "5"
%o A074340   while len(alst) < terms:
%o A074340     an = alst[-1] + 2
%o A074340     while an%5 ==0 or not isprime(int(astr + str(an))): an += 2
%o A074340     alst, astr = alst + [an], astr + str(an)
%o A074340   return alst
%o A074340 print(aupton(48)) # _Michael S. Branicky_, May 09 2021
%Y A074340 Cf. A069606, A046254, A074336, A074338, A074339, A074341, A074342, A074343, A074344, A074345, A074346.
%K A074340 nonn,base
%O A074340 1,1
%A A074340 _Zak Seidov_, Sep 23 2002
%E A074340 More terms from _Robert G. Wilson v_, Aug 05 2005