A316865 - OEIS

%I #11 Aug 11 2018 14:08:07

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

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

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

%N Number of times 4 appears in decimal expansion of n.

%e a(0) = 0 since the decimal representation of 0 does not contain the digit 4.

%e a(4) = 1 since 4 appears once in the decimal expansion of 4.

%t Array[ DigitCount[#, 10, 4] &, 105, 0]

%o (PARI) a(n) = #select(x->x==4, digits(n)); \\ _Michel Marcus_, Jul 20 2018

%Y Cf. A043505, A043506, A043507, A043508.

%Y Cf. A055641, A268643, A316863, A316864, A316866, A316867, A316868, A316869, A102683.

%K base,easy,nonn

%O 0,45

%A _Robert G. Wilson v_, Jul 15 2018