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A090537 Least n-digit prime using digit 3 once and rest all 1, or 0 if no such prime exists.

%I A090537 #13 Mar 14 2021 05:16:57
%S A090537 3,13,113,0,11113,113111,0,11111131,111111113,0,11111111113,
%T A090537 111113111111,0,31111111111111,0,0,11111111113111111,
%U A090537 111111111111111131,0,11111111111111111131,131111111111111111111,0,11111111111111111311111
%N A090537 Least n-digit prime using digit 3 once and rest all 1, or 0 if no such prime exists.
%F A090537 a(3n+1) = 0.
%o A090537 (Python)
%o A090537 from sympy import isprime
%o A090537 def agen():
%o A090537   digits = 0
%o A090537   while True:
%o A090537     for i in range(digits+1):
%o A090537       t = int("1"*(digits-i) + "3" + "1"*i)
%o A090537       if isprime(t): yield t; break
%o A090537     else: yield 0
%o A090537     digits += 1
%o A090537 g = agen()
%o A090537 print([next(g) for i in range(23)]) # _Michael S. Branicky_, Mar 13 2021
%Y A090537 Cf. A090535, A090536, A090538.
%Y A090537 Without zeros, subsequence of A107689.
%K A090537 base,nonn
%O A090537 1,1
%A A090537 _Amarnath Murthy_, Dec 08 2003
%E A090537 More terms from _David Wasserman_, Jan 03 2006