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

0,23

Links

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

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

Example

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.

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]

Prog

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

Crossrefs

Cf. A000027, A001477.

Cf. A043497, A043498, A043499, A043500.

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

Sequence in context: A173120 A025920 A037821 * A037911 A176046 A172090

Adjacent sequences: A316860 A316861 A316862 * A316864 A316865 A316866

Keyword

base,easy,nonn

Author

Robert G. Wilson v, Jul 15 2018

Status

approved