A316865 Number of times 4 appears in decimal expansion of n.

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, 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, 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

Offset: 0

Author

Robert G. Wilson v, Jul 15 2018

Keywords

• base
• easy
• nonn

Examples

			a(0) = 0 since the decimal representation of 0 does not contain the digit 4.
a(4) = 1 since 4 appears once in the decimal expansion of 4.
		

Crossrefs

Cf. A043505, A043506, A043507, A043508.

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

Programs

Mathematica

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

PARI

a(n) = #select(x->x==4, digits(n)); \\ Michel Marcus, Jul 20 2018