cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A182680 a(n) = the largest n-digit number with exactly 10 divisors, a(n) = 0 if no such number exists.

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%I A182680 #8 Mar 30 2012 19:00:24
%S A182680 0,80,976,9904,99952,999952,9999952,99999824,999999536,9999999824,
%T A182680 99999999536,999999999567,9999999999963,99999999999728,
%U A182680 999999999999856,9999999999998896,99999999999999824,999999999999999952,9999999999999999856,99999999999999999568
%N A182680 a(n) = the largest n-digit number with exactly 10 divisors, a(n) = 0 if no such number exists.
%C A182680 a(n) = the largest n-digit number of the form p^9 or p^4*q (p, q distinct primes), a(n) = 0 if no such number exists.
%F A182680 A000005(a(n)) = 10.
%F A182680 a(n) >= A182679(n).
%t A182680 Table[k=10^n-1; While[k>10^(n-1) && DivisorSigma[0, k] != 10, k--]; If[k==10^(n-1), k=0]; k, {n, 20}]
%Y A182680 Cf. A030628, A182679.
%K A182680 nonn,base
%O A182680 1,2
%A A182680 _Jaroslav Krizek_, Nov 27 2010
%E A182680 Extended by _T. D. Noe_, Nov 29 2010