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Position of the first 9 in the decimal expansion of the square root of n, or -1 if 9 never appears.
0

%I #5 Oct 01 2013 21:35:19

%S -1,-1,15,18,-1,8,4,15,15,-1,16,9,24,14,14,5,-1,19,13,6,8,9,3,3,3,-1,

%T 3,3,3,27,22,17,10,19,5,2,-1,12,11,5,20,58,9,25,7,8,7,20,2,-1,33,16,

%U 11,7,7,6,24,4,14,22,5,7,19,2,-1,12,14,16,18,11,19,7,18,31,22,31,6,5,29,6,2,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,-1

%N Position of the first 9 in the decimal expansion of the square root of n, or -1 if 9 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