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A167503
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Positions of nonzero digits in this sequence, where the terms are written in base 3 (and concatenated).
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4
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1, 2, 10, 12, 20, 21, 100, 101, 102, 112, 121, 122, 201, 202, 210, 211, 212, 220, 221, 222, 1000, 1001, 1002, 1011, 1012, 1021, 1022, 1100, 1102, 1110, 1111, 1112, 1120, 1121, 1122, 1200, 1202, 1210, 1211, 1212, 1220, 1221, 1222, 2010, 2020, 2021, 2101
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OFFSET
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1,2
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COMMENTS
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This sequence lists the positions of nonzero digits in the sequence, where the terms are written in base 3 and concatenated, such that the least significant digit (units) of a(n) is followed by the most significant digit of a(n+1).
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LINKS
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Table of n, a(n) for n=1..47.
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EXAMPLE
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The list cannot start with 0 (cf. A167500), so the first digit of the sequence is nonzero, whence a(1)=1.
The next nonzero digit of this sequence will be the most significant digit (m.s.d.) of a(2), necessarily nonzero, thus a(2)=2.
For the same reason, a(3) = 3[10] = 10[3]. (All terms are written in base 3.)
Thus the 4th digit is zero, followed by the m.s.d. of the next term which is nonzero, thus a(4)=5.
Terms of the sequence:_ 1,2,10,12,20,21,100,101
Position of the digits: 1 2 34 56 78 9A BCD EFG (A=10,...)
Thus the numbers 4,8,12,13,15,..., which give the positions of digits '0', are not in this sequence.
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PROG
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(PARI) base(n, b=3, s=1) = { my( a=[ n%b ]); while( 0<n\=b, a=concat( n%b, a )); if( s, eval( Strchr( vectorsmall( #a, i, 48+a[i] ))), a) }
{a=b=[]; for(n=1, 99, #b>=n & for(i=a[n-1]+1, #b, b[i] & (a=concat(a, i)) & break); #a<n & a=concat(a, #b+1); b=concat(b, base(a[n], 3, 0))); apply(base, a)}
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CROSSREFS
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Sequence in context: A053069 A178504 A193733 * A130842 A061818 A166938
Adjacent sequences: A167500 A167501 A167502 * A167504 A167505 A167506
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KEYWORD
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nonn,base
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AUTHOR
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M. F. Hasler, Nov 05 2009
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EXTENSIONS
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Edited by Charles R Greathouse IV, Aug 02 2010
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STATUS
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approved
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