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A182696 a(n) = the largest 4-digit number with exactly n divisors, a(n) = 0 if no such number exists. 1

%I

%S 0,9973,9409,9998,2401,9981,0,9994,9025,9904,1024,9999,4096,9664,9801,

%T 9982,0,9972,0,9968,7744,7168,0,9975,1296,0,6400,9920,0,9680,0,9990,

%U 9216,0,5184,9996,0,0,0,9936,0,9792,0,0,8100,0,0,9828,0,9072,0,0,0,9900,0,8640,0,0,0,9360,0,0,0,9240

%N a(n) = the largest 4-digit number with exactly n divisors, a(n) = 0 if no such number exists.

%C Among all 4-digit numbers, 64 is the maximum number of divisors, so a(64) is the last nonzero term.

%F A000005(a(n)) = n for a(n) > 0.

%t tbl=Table[{n,DivisorSigma[0,n]},{n,1000,9999}];

%t Table[Max[Transpose[Select[tbl,#[[2]]==x&]][[1]]],{x,70}]/.-\[Infinity]->0//Quiet (* _Harvey P. Dale_, Dec 02 2010 *)

%Y Cf. A182695.

%K nonn,base,fini,full

%O 1,2

%A _Jaroslav Krizek_, Nov 27 2010

%E Edited by _Jon E. Schoenfield_, Mar 11 2014

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Last modified September 23 04:23 EDT 2020. Contains 337294 sequences. (Running on oeis4.)