The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A182672 a(n) = the largest n-digit number with exactly 6 divisors, a(n) = 0 if no such number exists. 1

%I

%S 0,99,981,9981,99997,999981,9999988,99999961,999999981,9999999908,

%T 99999999964,999999999927,9999999999884,99999999999932,

%U 999999999999908,9999999999999925,99999999999999963,999999999999999929,9999999999999999999,99999999999999999916

%N a(n) = the largest n-digit number with exactly 6 divisors, a(n) = 0 if no such number exists.

%C a(n) = the largest n-digit number of the form p^5 or p^2*q^1, (p, q = distinct primes), a(n) = 0 if no such number exists.

%F A000005(a(n)) = 6.

%t Table[k=10^n-1; While[k>10^(n-1) && DivisorSigma[0, k] != 6, k--]; If[k==10^(n-1), k=0]; k, {n, 20}]

%Y Cf. A182671 (smallest n-digit number with exactly 6 divisors).

%K nonn,base

%O 1,2

%A _Jaroslav Krizek_, Nov 27 2010

%E Extended by _T. D. Noe_, Nov 29 2010

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 1 18:31 EST 2022. Contains 358475 sequences. (Running on oeis4.)