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Search: id:A124607
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| A124607 |
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Position of the first 7 in the decimal expansion of the square root of n, or -1 if 7 never appears. |
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+0
1
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| -1, -1, 12, 2, -1, 7, 8, 5, 7, -1, 6, 8, 13, 9, 2, 3, -1, 13, 10, 15, 3, 6, 8, 2, 6, -1, 14, 11, 28, 10, 3, 4, 23, 2, 18, 6, -1, 5, 15, 7, 14, 10, 5, 4, 11, 2, 2, 24, 12, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, -1, 7, 47, 8, 26, 15, 14, 8, 9, 8, 10, 10, 2, 2, 5, 10, 6, -1, 13, 9, 21, 10, 3, 4, 28, 27, 16, 52, 24, 8, 8, 2, 2, 7, 31, 6, -1
(list; graph; listen)
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OFFSET
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0,3
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PROGRAM
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(PARI) digitpos(n, m) = /* m-th digit in sqrt expansions */ { local(x, y, r, dot); default(realprecision, 1000); for(x=0, n, r = sqrt(x); if(issquare(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) = /* Revised 2007 */ { local(lnm, lns, tstr, vstr, x, j); vstr=Vec(Str(str)); match=Str(match); lns=length(str); lnm=length(match); for(x=1, lns-lnm+1, tstr=""; for(j=x, x+lnm-1, tstr=concat(tstr, vstr[j]); ); if(match==tstr, return(x)) ); return(0); }
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CROSSREFS
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Adjacent sequences: A124604 A124605 A124606 this_sequence A124608 A124609 A124610
Sequence in context: A075072 A038327 A010204 this_sequence A010205 A080496 A098781
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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 22 2006, corrected Jul 18 2007
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