%I #10 May 30 2021 11:10:01

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

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

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

%N Number of 4's in decimal expansion of prime(n).

%H Reinhard Zumkeller, <a href="/A085978/b085978.txt">Table of n, a(n) for n = 1..10000</a>

%t DigitCount[#,10,4]&/@Prime[Range[110]] (* _Harvey P. Dale_, May 30 2021 *)

%o (Haskell)

%o a085978 = count4 0 . a000040 where

%o count4 c x | d == 4 = if x < 10 then c + 1 else count4 (c + 1) x'

%o | otherwise = if x < 10 then c else count4 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, 3's A085977, 5's A085979, 6's A085980, 7's A085981, 8's A085982, 9's A085983.

%K base,nonn

%O 1,86

%A _Jason Earls_, Jul 06 2003