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A023719 Numbers with exactly two 3's in base 4 expansion. 1
15, 31, 47, 51, 55, 59, 60, 61, 62, 79, 95, 111, 115, 119, 123, 124, 125, 126, 143, 159, 175, 179, 183, 187, 188, 189, 190, 195, 199, 203, 204, 205, 206, 211, 215, 219, 220, 221, 222, 227, 231, 235, 236, 237, 238, 240, 241, 242, 244, 245, 246, 248, 249, 250 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..54.

EXAMPLE

62 in base 4 is 332. As that has precisely two 3's, 62 is in the sequence.

63 in base 4 is 333. As that has one more 3 than specified, 63 is not in the sequence.

MAPLE

select(k-> numboccur(3, convert(k, base, 4))=2, [$0..500])[];  # Alois P. Heinz, Feb 22 2019

MATHEMATICA

Select[Range[260], Count[IntegerDigits[#, 4], 3] == 2 &]

CROSSREFS

Sequence in context: A041440 A042017 A043346 * A031467 A045063 A044076

Adjacent sequences:  A023716 A023717 A023718 * A023720 A023721 A023722

KEYWORD

nonn,base,easy

AUTHOR

Olivier Gérard

STATUS

approved

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Last modified October 23 04:06 EDT 2021. Contains 348211 sequences. (Running on oeis4.)