cp's OEIS Frontend

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

%I A114344 #18 Jun 18 2023 08:44:54
%S A114344 1,1,5,3,-1,37,39,5,2,-1,89,20,52,222,319,49,-1,12,99,25,144,61,41,9,
%T A114344 109,-1,145,10,268,33,189,184,155,371,45,108,-1,118,26,11,149,146,108,
%U A114344 5,235,49,299,253,32,-1,103,212,120,179,353,119,225,64,10,108,104
%N A114344 Starting position of the first n in the decimal expansion of the square root of n, or -1 if n never appears.
%e A114344 For n=5, sqrt(5) = 2.23606797749978969640917366873127623544...
%e A114344 5 occurs in the 37th position so 37 is the 6th entry in the table counting from the 0th entry.
%o A114344 (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",") ) ) }
%o A114344 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); }
%Y A114344 Cf. A002193, A002194, A002163, A010464, A010465, A010466, A010467.
%K A114344 base,easy,sign
%O A114344 0,3
%A A114344 _Cino Hilliard_, Dec 22 2006, corrected Jul 18 2007