OFFSET
0,3
LINKS
Chai Wah Wu, Table of n, a(n) for n = 0..10000
EXAMPLE
For n = 8, cube root of 8 = 2, so 8 never appears.
For n = 12, cube root of 12 =2.28942848510666...77233158752412..., the first 12 starts in position 144.
For n = 31, cube root of 31 = 3.1413806..., the first 31 start in position 1. a(10^(3m)) = 1. - Chai Wah Wu, Oct 15 2016
PROG
(PARI) digitposcbrt2(n) = \ First n in the cbrt expansion of n { local(x, y, r, dot); for(x=0, n, r = (x^(1/3)); if(iscube(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) = \Return the position of the first occurrence of string \match in string str { local(lnm, lns, x, c, i); str=Str(str); \This allows leaving quotes off input match=Str(match); c=0; i=0; lns=length(str); lnm=length(match); if(lnm>1, i=1); x=1; while(x<=lns-lnm+1, if(mid(str, x, lnm)== match, break, x++); ); if(x>lns, return(0), return(x)) } mid(str, s, n) = \ Get a substring of length n from string str starting at position s in str. { local(v, ln, x, tmp); v =""; tmp = Vec(str); ln=length(tmp); for(x=s, s+n-1, v=concat(v, tmp[x]); ); return(v) } iscube(n) = { local(r); r = n^(1/3); if(floor(r+.5)^3== n, 1, 0) }
CROSSREFS
KEYWORD
base,easy,sign
AUTHOR
Cino Hilliard, Dec 25 2006
EXTENSIONS
Corrected a(27), a(31) and a(64) by Chai Wah Wu, Oct 15 2016
STATUS
approved