Search: id:A081512
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%I A081512
%S A081512 1,0,6,12,24,24,48,60,84,120,120,120,180,180,240,360,360,360,360,672,
%T A081512 720,720,720,840,840,1080,1260,1260,1260,1680,1680,1680,2160,2520,2520,
%U A081512 2520,2520,2520,2520,3360,4320,5040,5040,5040,5040,5040,5040,5040,5040
%N A081512 a(n) = smallest number which can be expressed as the sum of n of its 
               distinct divisors. In the following triangle the n-th row contains 
               the n divisors pertaining to the this sequence. a(n) = sum of the 
               n-th row.
%C A081512 1
%C A081512 - -
%C A081512 1 2 3
%C A081512 1 2 3 6
%C A081512 1 2 3 6 12
%C A081512 1 2 3 4 6 8
%C A081512 1 2 3 6 8 12 16
%e A081512 a(2) = 0. All other entries are nonzero.
%e A081512 24 is a sum of 6 of its divisors. Namely, 1+2+3+4+6+8=24. Furthermore, 
               24 is the smallest natural number with at least 6 divisors (not including 
               itself), so it must be the smallest natural number that is a sum 
               of 6 of its divisors.
%p A081512 A081512 := proc(n) local a, dvs, dset,s,p; if n= 2 then RETURN(0) ; end 
               if; for a from 1 do dvs := numtheory[divisors](a) ; dset := combinat[choose](dvs,
               n) ; for s in dset do if add(p,p=s) = a then RETURN(a) ; end if; 
               end do; end do: end: for n from 2 do a := A081512(n) ; printf("%d, 
               ",a) ; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 
               11 2008]
%Y A081512 Cf. A081513, A081514.
%Y A081512 Sequence in context: A144568 A078472 A005694 this_sequence A096387 A094185 
               A074902
%Y A081512 Adjacent sequences: A081509 A081510 A081511 this_sequence A081513 A081514 
               A081515
%K A081512 nonn
%O A081512 1,3
%A A081512 Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 27 2003
%E A081512 Corrected by Caleb M. Shor (cshor(AT)bates.edu), Sep 26 2007
%E A081512 Extended beyond a(7) by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Nov 11 2008
%E A081512 a(16)-a(49) from Max Alekseyev (maxale(AT)gmail.com), Jul 27 2009

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