Search: id:A130520
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%I A130520
%S A130520 0,0,0,0,0,1,2,3,4,5,7,9,11,13,15,18,21,24,27,30,34,38,42,46,50,55,60,
%T A130520 65,70,75,81,87,93,99,105,112,119,126,133,140,148,156,164,172,180,189,
%U A130520 198,207,216,225,235,245,255,265,275,286,297,308,319,330,342,354,366
%N A130520 Sum {0<=k<=n, floor(k/5)} (Partial sums of A002266).
%C A130520 Complementary with A130483 regarding triangular numbers, in that A130483(n)+5*a(n)=n(n+1)/
               2=A000217(n).
%F A130520 a(n)=1/2*floor(n/5)*(2n-3-5*floor(n/5))=A002266(n)*(2n-3-5*A002266(n))/
               2. Also: a(n)=1/2*A002266(n)*(n-3+A010874(n)). G.f.: g(x)=x^5/((1-x^5)(1-x)^2).
%F A130520 a(n) = floor((n-1)(n-2)/10) [From Mitch Harris (maharri(AT)gmail.com), 
               Sep 08 2008]
%F A130520 a(n)=A008732(n-5), n>4. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Nov 22 2008]
%Y A130520 Cf. A002264, A002265, A004526, A010872, A010873, A010874, A130481, A130482.
%Y A130520 Sequence in context: A051532 A135785 A008732 this_sequence A005706 A064175 
               A000028
%Y A130520 Adjacent sequences: A130517 A130518 A130519 this_sequence A130521 A130522 
               A130523
%K A130520 nonn
%O A130520 0,7
%A A130520 Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), Jun 01 2007

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