Search: id:A126073
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%I A126073
%S A126073 0,0,3,3,8,14,14,14,23,33,33,45,45,45,45,45,45,63,63,83,104,104,104,128,
%T A126073 153,153,180,180,180,180,180,180,213,213,248,284,284,284,323,363,363,
%U A126073 405,405,405,405,405,405,453,453,503,554,554,554,608,663,663,720,720
%N A126073 Sum of numbers <= n which are multiples of 3 or 5 but not 15.
%C A126073 Sum of numbers m<=n such that mod(m,3)*mod(m,5)=0 and mod(m,15)>0.
%C A126073 First differences (fd) are
%C A126073 0,3,0,5,6,0,0,9,10,0,12,0,0,0,0,
%C A126073 0,18,0,20,21,0,0,24,25,0,27,0,0,0,0,
%C A126073 0,33,0,35,36,0,0,39,40,0,42,0,0,0,0,...
%C A126073 fd(1..15)={0,3,0,5,6,0,0,9,10,0,12,0,0,0,0}; for n>15
%C A126073 fd(n)=fd(n-15)+15 if fd(n-15)>0, fd(n)=0 otherwise.
%F A126073 an[n,d]=d*Floor[n/d];sn[n,d]=(an[n,d]*(an[n,d] + d))/(2*d); a(n)=sn[n,
               3]+sn[n,5]-2*sn[n,15].
%t A126073 an[n_,d_]:=d*Floor[n/d];sn[n_,d_]:=(an[n,d]*(an[n,d] + d))/(2*d); Table[sn[n,
               3]+sn[n,5]-2*sn[n,15],{n,1000}]
%Y A126073 Cf. A126590, A126592.
%Y A126073 Sequence in context: A052407 A105039 A090597 this_sequence A126592 A055057 
               A154029
%Y A126073 Adjacent sequences: A126070 A126071 A126072 this_sequence A126074 A126075 
               A126076
%K A126073 nonn
%O A126073 1,3
%A A126073 Zak Seidov (zakseidov(AT)gmail.com), Mar 13 2007

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