A085977 - OEIS

%I #10 Aug 05 2019 18:17:12

%S 0,1,0,0,0,1,0,0,1,0,1,1,0,1,0,1,0,0,0,0,1,0,1,0,0,0,1,0,0,1,0,1,1,1,

%T 0,0,0,1,0,1,0,0,0,1,0,0,0,1,0,0,2,1,0,0,0,1,0,0,0,0,1,1,1,1,2,1,2,2,

%U 1,1,2,1,1,2,1,2,1,1,0,0,0,0,1,2,1,1,0,0,0,1,0,0,0,0,0,1,0,0,1,0,0,0,1,0,0

%N Number of 3's in decimal expansion of prime(n).

%H Reinhard Zumkeller, <a href="/A085977/b085977.txt">Table of n, a(n) for n = 1..10000</a>

%e prime(2) = 3, so a(2)=1 and prime(345) = 2333, so a(345)=3.

%t DigitCount[Prime[Range[110]],10,3] (* _Harvey P. Dale_, Aug 05 2019 *)

%o (Haskell)

%o a085977 = count3 0 . a000040 where

%o    count3 c x | d == 3    = if x < 10 then c + 1 else count3 (c + 1) x'

%o               | otherwise = if x < 10 then c else count3 c x'

%o               where (x', d) = divMod x 10

%o -- _Reinhard Zumkeller_, Apr 08 2014

%Y Cf. 0's A085974, 1's A085975, 2's A085976, 4's A085978, 5's A085979, 6's A085980, 7's A085981, 8's A085982, 9's A085983.

%K base,nonn

%O 1,51

%A _Jason Earls_, Jul 06 2003