A244255 a(n) = the frequency of the most common 2-digit ending of a prime with n digits.

1, 6, 31, 220, 1748, 14746, 127601, 1127869, 10107163, 91579392, 837273621

Offset

2,2

Links

Table of n, a(n) for n=2..12.

Example

Of the 3-digit primes, the most common two-digit ending occurs 6 times. Thus a(3) = 6.

Prog

(Python)
import sympy
from sympy import isprime
def end1(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)
  return max(lst)
n = 3
while n < 10:
  print(end1(2, n), end=', ')
  n += 1

Crossrefs

Cf. A244190.

Sequence in context: A121754 A351818 A200775 * A299550 A208594 A318539

Adjacent sequences: A244252 A244253 A244254 * A244256 A244257 A244258

Keyword

nonn,base,hard,more

Author

Derek Orr, Jun 24 2014

Extensions

a(8)-a(12) from Hiroaki Yamanouchi, Aug 26 2014

Status

approved