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Search: id:A023717
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| A023717 |
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Numbers with no 3's in base 4 expansion. |
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+0
1
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| 0, 1, 2, 4, 5, 6, 8, 9, 10, 16, 17, 18, 20, 21, 22, 24, 25, 26, 32, 33, 34, 36, 37, 38, 40, 41, 42, 64, 65, 66, 68, 69, 70, 72, 73, 74, 80, 81, 82, 84, 85, 86, 88, 89, 90, 96, 97, 98, 100, 101, 102, 104, 105, 106, 128, 129, 130, 132, 133
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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a(n)=Sum{d(i)*4^i: i=0, 1, ..., m}, where Sum{d(i)*3^i: i=0, 1, ..., m} is the base 3 representation of n. - Clark Kimberling (ck6(AT)evansville.edu)
a(3n)=4a(n); a(3n+1)=4a(n)+1; a(3n+2)=4a(n)+2; a(n)=4*a(floor(n/3))+n-3*floor(n/3) - Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 27 2003
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MATHEMATICA
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Select[ Range[ 0, 140 ], (Count[ IntegerDigits[ #, 4 ], 3 ]==0)& ]
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PROGRAM
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(PARI) a(n)=if(n<1, 0, if(n%3, a(n-1)+1, 4*a(n/3))) or a(n)=if(n<1, 0, 4*a(floor(n/3))+n-3*floor(n/3))
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CROSSREFS
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Adjacent sequences: A023714 A023715 A023716 this_sequence A023718 A023719 A023720
Sequence in context: A095775 A035063 A004128 this_sequence A043687 A087118 A039032
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KEYWORD
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nonn,base,easy
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AUTHOR
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Olivier Gerard (olivier.gerard(AT)gmail.com)
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