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A126206

Number of 4's in the decimal expansion of 4^n.

0, 1, 0, 1, 0, 1, 1, 1, 0, 2, 1, 3, 0, 1, 2, 2, 2, 1, 1, 3, 0, 3, 3, 3, 2, 2, 2, 3, 1, 2, 2, 3, 4, 3, 1, 3, 3, 4, 2, 4, 2, 4, 2, 2, 3, 4, 3, 3, 3, 3, 2, 2, 3, 5, 2, 4, 2, 4, 4, 3, 3, 3, 4, 4, 6, 5, 5, 4, 2, 9, 5, 2, 4, 6, 4, 7, 4, 2, 5, 4, 3, 4, 8, 4, 7, 9, 2, 8, 4, 7, 3, 10, 9, 5, 3, 5, 8, 8, 3, 10, 4

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OFFSET

0,10

LINKS

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

EXAMPLE

a(11)=3 because 4^11 = 4194304 with three 4's.

MAPLE

map(n -> numboccur(4, convert(4^n, base, 10)), [$0..100]); # Robert Israel, Jul 18 2018

MATHEMATICA

DigitCount[4^#, 10, 4]&/@Range[0, 150] (* Harvey P. Dale, Feb 01 2011 *)

CROSSREFS