%I A103977
%S A103977 1,1,2,1,4,0,6,1,5,2,10,0,12,4,6,1,16,1,18,0,10,8,22,0,19,10,14,0,28,0,
%T A103977 30,1,18,14,22,1,36,16,22,0,40,0,42,4,12,20,46,0,41,7,30,6,52,0,38,0,34,
%U A103977 26,58,0,60,28,22,1,46,0,66,10,42,0,70,1,72,34,26,12,58,0,78,0
%N A103977 Let d_1 ... d_k be the divisors of n. Then a(n) = min_{ e_1 = +-1, ... 
               e_k = +-1 } | Sum_i e_i d_i |
%F A103977 If n=p (prime), then a(n)=p-1. If n=2^m, then a(n)=1. [Corrected by R. 
               J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 27 2007]
%e A103977 a(6)=1+2+3-6=0
%p A103977 A103977 := proc(n) local divs,a,acandid,filt,i,p,sigs ; divs := convert(numtheory[divisors](n),
               list) ; a := add(i,i=divs) ; for sigs from 0 to 2^nops(divs)-1 do 
               filt := convert(sigs,base,2) ; while nops(filt) < nops(divs) do filt 
               := [op(filt), 0] ; od ; acandid := 0 ; for p from 0 to nops(divs)-1 
               do if op(p+1,filt) = 0 then acandid := acandid-op(p+1,divs) ; else 
               acandid := acandid+op(p+1,divs) ; fi ; od: acandid := abs(acandid) 
               ; if acandid < a then a := acandid ; fi ; od: RETURN(a) ; end: seq(A103977(n),
               n=1..80) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 27 
               2007
%Y A103977 Cf. A125732, A125733, A005835, A023196.
%Y A103977 Sequence in context: A087664 A158032 A120112 this_sequence A109883 A033880 
               A033879
%Y A103977 Adjacent sequences: A103974 A103975 A103976 this_sequence A103978 A103979 
               A103980
%K A103977 nonn
%O A103977 1,3
%A A103977 Yasutoshi Kohmoto zbi74583(AT)boat.zero.ad.jp, Jan 01 2007
%E A103977 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 27 2007