A316863 Number of times 2 appears in the decimal expansion of n.

0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0

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 2.
a(2) = 1 since 2 appears once in the decimal expansion of 2.
a(22) = 2 since 2 appears twice in the decimal expansion of 22.
		

Links

• Robert Israel, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A043497, A043498, A043499, A043500.

Cf. A055641, A268643, A316864, A316865, A316866, A316867, A316868, A316869, A102683.

Programs

Maple

f:= n -> numboccur(2,convert(n,base,10)):
map(f, [$0..200]); # Robert Israel, Apr 21 2020

Mathematica

Array[ DigitCount[#, 10, 2] &, 105, 0]

PARI

a(n) = #select(x->x==2, digits(n)); \\ Michel Marcus, Jul 20 2018

Formula

G.f.: (1-x)^(-1)*Sum_{k>=0} (x^(2*10^k)-x^(3*10^k))/(1-x^(10^(k+1))). - Robert Israel, Apr 21 2020