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%I #5 Oct 01 2013 21:35:19
%S -1,-1,9,12,-1,4,39,2,13,-1,3,4,3,2,5,10,-1,8,5,14,30,8,2,27,12,-1,39,
%T 4,8,6,14,3,2,6,37,4,1,1,1,1,1,1,1,1,1,1,1,1,1,-1,6,30,19,41,6,4,21,
%U 17,2,2,6,8,20,27,-1,3,11,18,4,4,3,4,48,18,2,2,24,6,6,26,20,-1,16,23,3,30,5,34,11,13,4,12,5,2,2,4,25,13,10,12,-1
%N Position of the first 6 in the decimal expansion of the square root of n, or -1 if 6 never appears.
%o (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); }
%K base,easy,sign
%O 0,3
%A _Cino Hilliard_, Dec 22 2006, corrected Jul 18 2007
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