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Largest number whose cube has n digits.
15

%I #18 Jun 09 2019 21:14:46

%S 2,4,9,21,46,99,215,464,999,2154,4641,9999,21544,46415,99999,215443,

%T 464158,999999,2154434,4641588,9999999,21544346,46415888,99999999,

%U 215443469,464158883,999999999,2154434690,4641588833,9999999999

%N Largest number whose cube has n digits.

%C a(n) + A181375(n) + A181377(n) + A181379(n) + A181381(n) + A181400(n) + A181402(n) + A181404(n) + A130130(n) = A002283(n).

%F a(n) = ceiling(10^(n/3)) - 1. - Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 30 2003

%e a(5) = 46 because 46^3 = 97336 has 5 digits, while 47^3 = 103823 has 6 digits.

%p Digits := 100:

%p A061439 := n->ceil(10^(n/3))-1:

%p seq (A061439(n), n=1..40);

%t t={}; i=0; Do[i=i+1; While[IntegerLength[i^3]<=n,i++]; AppendTo[t,i-1],{n,20}]; t (* _Jayanta Basu_, May 19 2013 *)

%Y a(n) is one more than the corresponding term of A018005. Cf. A061435.

%K nonn,base,easy

%O 1,1

%A _Amarnath Murthy_, May 03 2001

%E More terms from Larry Reeves (larryr(AT)acm.org), May 16 2001

%E Typo in Maple program fixed by _Martin Renner_, Jan 31 2011