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A124688 Position of the first n in the decimal expansion of the cube root of n, or -1 if the digits of n never appear. 1
1, 1, 2, 11, 5, 7, 17, 11, -1, 14, 50, 19, 144, 4, 5, 29, 56, 228, 164, 13, 35, 33, 161, 62, 377, 58, 60, -1, 164, 17, 69, 1, 154, 46, 93, 229, 54, 103, 134, 2, 88, 347, 53, 22, 71, 211, 15, 68, 37, 718, 74, 26, 68, 77, 42, 43, 35, 241, 188, 90, 25, 212, 85, 13, -1, 22, 165, 14, 260, 82, 44, 33, 36, 176, 66, 26, 40, 17, 58, 72, 9, 156 (list; graph; refs; listen; history; text; internal format)
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

Sequence in context: A077272 A009301 A087552 * A158616 A127821 A114724

Adjacent sequences:  A124685 A124686 A124687 * A124689 A124690 A124691

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

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Last modified September 20 10:32 EDT 2019. Contains 327229 sequences. (Running on oeis4.)