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A070844 a(n) = smallest n-digit number with exactly n divisors, or 0 if no such number exists. 6

%I #10 Dec 05 2013 19:55:19

%S 1,11,121,1003,14641,100017,1771561,10000005,100020001,1000000016,

%T 25937424601,100000000004,3138428376721,10000000001344,

%U 100000720001296,1000000000000006,45949729863572161,100000000000000404

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

%H Ray Chandler, <a href="/A070844/b070844.txt">Table of n, a(n) for n=1..41</a>

%F If n is a prime < 29 then a(n) = 11^(n-1). - Chandler

%F If n is a prime >= 29 then a(n) = 0. - _Vladeta Jovovic_, Aug 20 2002

%t For[n=1, n<10, n++, k := 10^(n-1); While[Not[Length[Divisors[k]] == n], k++ ]; Print[k]] (Steinerberger)

%Y Cf. A070845.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, May 12 2002

%E a(6)-a(18) from _Vladeta Jovovic_, Aug 20 2002

%E a(6) confirmed by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 08 2003

%E a(7)-a(10) confirmed by _Stefan Steinerberger_, Feb 06 2006

%E a(15) corrected, and a(11)-a(14), a(16)-a(18) confirmed by _Ray Chandler_, Feb 10 2009

%E Edited by _N. J. A. Sloane_, Feb 14 2009 at the suggestion of Ray Chandler.

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Last modified May 3 08:32 EDT 2024. Contains 372207 sequences. (Running on oeis4.)