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Search: id:A124686
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| A124686 |
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Position of the first 1 in the decimal expansion of the cube root of n, or -1 if this digit never appears. |
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+0
1
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| -1, 1, 1, 1, 1, 1, 1, 1, -1, 13, 2, 15, 11, 4, 3, 6, 3, 4, 7, 7, 3, 8, 17, 13, 8, 6, 26, -1, 10, 6, 2, 2, 2, 24, 6, 4, 4, 7, 4, 4, 3, 6, 27, 17, 20, 23, 10, 11, 7, 9, 7, 14, 6, 13, 8, 13, 44, 7, 21, 9, 3, 8, 7, 16, -1, 27, 4, 4, 4, 2, 2, 2, 2, 2, 2, 3, 17, 11, 10, 17, 21, 9, 7, 10, 6, 11, 3, 4, 8, 28, 4, 7, 3, 45, 22, 35, 12, 38, 3, 11, 4
(list; graph; listen)
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OFFSET
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0,10
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PROGRAM
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(PARI) digitposcbrt(n, m) = \ cbrt expansion { local(x, y, r, dot); for(x=0, n, r = (x^(1/3)); if(iscube(x), y=find(Str(floor(r)), m), y=find(Str(r), m); dot=find(Str(r), "."); if(dot < y, y--); ); if(y, print1(y", "), print1(-1", ") ) ) } find(str, match) = \Return the position of the first occurrence of string \match in string str { local(lnm, lns, x, c, i); str=Str(str); \This allows leaving quotes off input match=Str(match); c=0; i=0; lns=length(str); lnm=length(match); if(lnm>1, i=1); x=1; while(x<=lns-lnm+1, if(mid(str, x, lnm)== match, break, x++); ); if(x>lns, return(0), return(x)) } mid(str, s, n) = \ Get a substring of length n from string str starting at position s in str. { local(v, ln, x, tmp); v =""; tmp = Vec(str); ln=length(tmp); for(x=s, s+n-1, v=concat(v, tmp[x]); ); return(v) } iscube(n) = { local(r); r = n^(1/3); if(floor(r+.5)^3== n, 1, 0) }
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CROSSREFS
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Adjacent sequences: A124683 A124684 A124685 this_sequence A124687 A124688 A124689
Sequence in context: A100081 A078197 A070704 this_sequence A113807 A008832 A040168
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KEYWORD
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base,easy,sign
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AUTHOR
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Cino Hilliard (hillcino368(AT)hotmail.com), Dec 24 2006
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