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A316863
Number of times 2 appears in the decimal expansion of n.
9
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
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
KEYWORD
base,easy,nonn
AUTHOR
Robert G. Wilson v, Jul 15 2018
STATUS
approved