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A244190 a(n) = most common 2-digit ending for a prime with n digits, or 0 if there is a tie. 2
0, 57, 0, 97, 71, 93, 59, 73, 47, 51, 19, 27 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

21 and 23 are tied with 4-digit primes so a(4) = 0.

LINKS

Table of n, a(n) for n=2..13.

EXAMPLE

Of the primes with 3 digits, the most common 2 digit ending is 57. Thus a(3) = 57.

PROG

(Python)

import sympy

from sympy import isprime

def end(d, n):

..lst = []

..for k in range(10**(d-1), 10**d):

....num = ''

....count = 0

....for i in range(10**(n-d-1), 10**(n-d)):

......if isprime(int(str(i)+str(k))):

........count += 1

....lst.append(count)

..a = max(lst)

..lst[lst.index(a)] = 0

..b = max(lst)

..if a == b:

....return 0

..else:

....return max(a, b) + 10**(d-1)

n = 3

while n < 10:

..print(end(2, n), end=', ')

..n += 1

CROSSREFS

Cf. A244189.

Sequence in context: A101355 A285179 A307938 * A013682 A278068 A126828

Adjacent sequences:  A244187 A244188 A244189 * A244191 A244192 A244193

KEYWORD

nonn,base,hard,more

AUTHOR

Derek Orr, Jun 22 2014

EXTENSIONS

a(9) from Tom Edgar, Jun 24 2014

a(10)-a(12) from Hiroaki Yamanouchi, Jul 11 2014

a(13) from Marek Hubal, Mar 04 2019

STATUS

approved

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Last modified July 12 08:23 EDT 2020. Contains 335657 sequences. (Running on oeis4.)