A063272 Number of times most common final digit of primes appears in first n primes.

1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 17, 17, 17, 18, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 21, 21, 21, 21, 21, 21

Offset: 1

Author

Henry Bottomley, Jul 13 2001

Keywords

• base
• nonn

Examples

			a(6)=2 since first six primes are 2,3,5,7,11,13, so most common final digit is 3 which has appeared twice.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to final digits of numbers

Crossrefs

Cf. A000040, A007652, A063272. Slightly above floor(n/4), i.e., A002265.

Programs

Maple

V:= Vector(9):
p:= 1:
for n from 1 to 100 do
  p:= nextprime(p);
  r:= p mod 10;
  V[r]:= V[r]+1;
  A[n]:= max(V)
od:
seq(A[i],i=1..100); # Robert Israel, Jul 22 2018

Formula

a(n) ~ n/phi(10) = n/4 by the Prime Number Theorem in Arithmetic Progressions. - Charles R Greathouse IV, Dec 29 2012