A124604 Position of the first 4 in the decimal expansion of the square root of n, or -1 if 4 never appears.

-1, -1, 2, 23, -1, 11, 2, 3, 5, -1, 27, 7, 2, 11, 3, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, -1, 16, 8, 38, 7, 2, 7, 7, 3, 10, 18, -1, 25, 4, 3, 4, 2, 2, 5, 6, 11, 22, 7, 19, -1, 14, 3, 23, 26, 3, 2, 2, 3, 23, 6, 3, 6, 4, 22, -1, 9, 4, 14, 3, 16, 12, 2, 2, 3, 12, 7, 15, 4, 15, 7, 3, -1, 14, 5, 25, 6, 8, 18, 12, 2, 2, 10, 9, 3, 10, 3, 69, 3, 5, 3, -1

Offset

0,3

Links

Table of n, a(n) for n=0..100.

Prog

(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); }

Crossrefs

Sequence in context: A343263 A261198 A052077 * A374376 A329336 A323396

Adjacent sequences: A124601 A124602 A124603 * A124605 A124606 A124607

Keyword

base,easy,sign

Author

Cino Hilliard, Dec 22 2006, corrected Jul 18 2007

Status

approved