This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A086670 #28 Feb 13 2023 16:06:23
%S A086670 0,1,1,3,2,5,3,7,5,8,5,13,6,11,10,15,8,18,9,20,14,17,11,29,14,20,18,
%T A086670 27,14,34,15,31,22,26,22,44,18,29,26,44,20,46,21,41,36,35,23,61,27,45,
%U A086670 34,48,26,58,34,59,38,44,29,82,30,47,49,63,40,70,33,62,46,70,35,96,36,56
%N A086670 Sum of floor(d/2) where d is a divisor of n.
%C A086670 Inverse Mobius transform of A004526. - _R. J. Mathar_, Jan 19 2009
%F A086670 G.f.: Sum_{n>=1} floor(n/2)*x^n/(1-x^n). - _Joerg Arndt_, Jan 30 2011
%F A086670 a(n) = (A000203(n) - A001227(n)) / 2. - _Franklin T. Adams-Watters_, Jan 05 2012
%F A086670 G.f.: Sum_{k>=1} x^(2*k) / ((1 + x^k) * (1 - x^k)^2). - _Ilya Gutkovskiy_, Aug 02 2021
%F A086670 a(n) = Sum_{i=1..floor(n/2)} A135539(n,2*i). - _Ridouane Oudra_, Apr 15 2022
%e A086670 10 has divisors 1,2,5,10. floor(d/2) gives 0,1,2,5, therefore a(10)=8.
%t A086670 Table[Total[Floor[Divisors[n]/2]],{n,80}] (* _Harvey P. Dale_, Feb 13 2023 *)
%o A086670 (PARI) for (n=1,100,s=0; fordiv(i=n,i,s+=floor(i/2)); print1(","s))
%o A086670 (PARI) a(n) = my(f = factor(n)); (sigma(f) - (numdiv(f)/(valuation(n, 2)+1)))>>1 \\ _David A. Corneth_, Apr 15 2022 using _Franklin T. Adams-Watters_'s formula
%Y A086670 Cf. A000203, A001227, A004526, A079247.
%Y A086670 Cf. A135539.
%K A086670 nonn
%O A086670 1,4
%A A086670 _Jon Perry_, Jul 27 2003