A114344 Starting position of the first n in the decimal expansion of the square root of n, or -1 if n never appears.

1, 1, 5, 3, -1, 37, 39, 5, 2, -1, 89, 20, 52, 222, 319, 49, -1, 12, 99, 25, 144, 61, 41, 9, 109, -1, 145, 10, 268, 33, 189, 184, 155, 371, 45, 108, -1, 118, 26, 11, 149, 146, 108, 5, 235, 49, 299, 253, 32, -1, 103, 212, 120, 179, 353, 119, 225, 64, 10, 108, 104

Offset: 0

Author

Cino Hilliard, Dec 22 2006, corrected Jul 18 2007

Keywords

• base
• easy
• sign

Examples

			For n=5, sqrt(5) = 2.23606797749978969640917366873127623544...
5 occurs in the 37th position so 37 is the 6th entry in the table counting from the 0th entry.
		

Crossrefs

Cf. A002193, A002194, A002163, A010464, A010465, A010466, A010467.

Programs

PARI

digitpos(n) = { local(x,y,r,dot); for(x=0,n, r=sqrt(x); if(issquare(x), y=find(Str(floor(r)),x), y=find(Str(r),x); 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); }