A085975 - OEIS

%I #12 Oct 30 2023 11:33:18

%S 0,0,0,0,2,1,1,1,0,0,1,0,1,0,0,0,0,1,0,1,0,0,0,0,0,2,1,1,1,2,1,2,1,1,

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

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

%N Number of 1's in decimal expansion of prime(n).

%H Reinhard Zumkeller, <a href="/A085975/b085975.txt">Table of n, a(n) for n = 1..10000</a>

%e prime(5) = 11, so a(5)=2 and prime(1242) = 10111, so a(1242)=4.

%t DigitCount[Prime[Range[100]],10,1] (* _Paolo Xausa_, Oct 30 2023 *)

%o (Haskell)

%o a085975 = count1 0 . a000040 where

%o    count1 c x | d == 1    = if x < 10 then c + 1 else count1 (c + 1) x'

%o               | otherwise = if x < 10 then c else count1 c x'

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

%o -- _Reinhard Zumkeller_, Apr 08 2014

%Y Cf. 0's A085974, 2's A085976, 3's A085977, 4's A085978, 5's A085979, 6's A085980, 7's A085981, 8's A085982, 9's A085983.

%K base,nonn

%O 1,5

%A _Jason Earls_, Jul 06 2003