OFFSET
2,4
COMMENTS
a(3) = 0 because '83' and '57' both appear 6 times in the endings of primes < 1000.
a(4) = 0 because '19' and '23' both appear 35 times in the endings of primes < 10000.
EXAMPLE
For all primes < 100000 (10^5), the most common 2-digit ending is 97. Thus a(5) = 97.
PROG
(Python)
import sympy
from sympy import isprime
def prend(d, n):
..lst = []
..for k in range(10**n):
....if isprime(k):
......lst.append((k%10**d))
..new = 0
..newlst = []
..for i in range(10**(d-1), 10**d):
....new = lst.count(i)
....newlst.append(new)
..newlst1 = newlst.copy()
..a = max(newlst1)
..newlst1[newlst1.index(a)] = 0
..b = max(newlst1)
..if a == b:
....return 0
..else:
....return newlst.index(max(a, b)) + 10**(d-1)
n = 3
while n < 10:
..print(prend(2, n), end=', ')
..n += 1
CROSSREFS
KEYWORD
nonn,base,hard,more
AUTHOR
Derek Orr, Jun 22 2014
EXTENSIONS
a(9)-a(12) from Hiroaki Yamanouchi, Jul 11 2014
a(13)-a(14) from Giovanni Resta, Oct 23 2018
STATUS
approved