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Search: id:A076127
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| A076127 |
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n-th term is binary string of length t_n with 1's at positions t_i, where t_n = n-th triangular number. |
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+0
3
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| 0, 1, 101, 101001, 1010010001, 101001000100001, 101001000100001000001, 1010010001000010000010000001, 101001000100001000001000000100000001, 101001000100001000001000000100000001000000001
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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if(n==0), a(0)=0; else a(n)=10^n*a(n-1)+1
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EXAMPLE
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For example, the first 4 strings are: '1' (length 1, nonzero index 1), '101' (length 3, nonzero indices 1,3), '101001' (length 6, nonzero indices 1,3,6) '1010010001' (length 10, nonzero indices 1,3,6,10)
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MATHEMATICA
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f[n_] := Block[{a = {1}}, Do[a = Join[a, Table[0, {i}], {1}], {i, 1, n}]; FromDigits[a]]; Table[ f[n], {n, 0, 8}]
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PROGRAM
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(PARI) a(n)=if(n<1, 0, 1+a(n-1)*10^n)
(MATLAB) function ans=bstn(n) if(n==0), ans=0; else, ans=10^n*bstn(n-1)
(PARI) {a(n)=if(n<0, 0, subst( Polrev( Vec( sum(k=1, n, x^(k*(k+1)/2)))), x, 10))}
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CROSSREFS
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Cf. A000217, A076131.
Sequence in context: A068160 A082435 A136098 this_sequence A138721 A015078 A031982
Adjacent sequences: A076124 A076125 A076126 this_sequence A076128 A076129 A076130
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KEYWORD
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easy,nonn,base
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AUTHOR
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Kyle Hunter (hunterk(AT)raytheon.com), Oct 31 2002
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 31 2002
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