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%I #36 Mar 04 2019 18:16:15
%S 0,57,0,97,71,93,59,73,47,51,19,27
%N a(n) = most common 2-digit ending for a prime with n digits, or 0 if there is a tie.
%C 21 and 23 are tied with 4-digit primes so a(4) = 0.
%e Of the primes with 3 digits, the most common 2 digit ending is 57. Thus a(3) = 57.
%o (Python)
%o import sympy
%o from sympy import isprime
%o def end(d,n):
%o ..lst = []
%o ..for k in range(10**(d-1),10**d):
%o ....num = ''
%o ....count = 0
%o ....for i in range(10**(n-d-1),10**(n-d)):
%o ......if isprime(int(str(i)+str(k))):
%o ........count += 1
%o ....lst.append(count)
%o ..a = max(lst)
%o ..lst[lst.index(a)] = 0
%o ..b = max(lst)
%o ..if a == b:
%o ....return 0
%o ..else:
%o ....return max(a,b) + 10**(d-1)
%o n = 3
%o while n < 10:
%o ..print(end(2,n),end=', ')
%o ..n += 1
%Y Cf. A244189.
%K nonn,base,hard,more
%O 2,2
%A _Derek Orr_, Jun 22 2014
%E a(9) from _Tom Edgar_, Jun 24 2014
%E a(10)-a(12) from _Hiroaki Yamanouchi_, Jul 11 2014
%E a(13) from _Marek Hubal_, Mar 04 2019
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