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 A299777 #11 Apr 24 2018 23:14:11 %S A299777 1,1,2,5,2,3,7,8,4,3,9,10,5,11,11,4,12,6,13,13,14,14,7,5,15,15,16,16, %T A299777 8,17,17,23,18,18,9,19,19,19,20,20,7,20,10,21,21,21,22,22,45,11,23,23, %U A299777 23,24,24,24,37,25,26,25,25,26,26,26,13,27,27,55,27,28,29,28,28,14,29,10,29,29,30,29 %N A299777 a(n) is the sum of middle divisors of the n-th number that has middle divisors. %C A299777 The middle divisors of n, are the divisors in the half-open interval [sqrt(n/2), sqrt(n*2)). %F A299777 a(n) = A071090(A071562(n)). %e A299777 For n = 12 the 12th number that has middle divisors is 24. The divisors of 24 are 1, 2, 3, 4, 6, 8, 12, 24. The middle divisors of 24 are 4 and 6, and the sum of them is 4 + 6 = 10, so a(12) = 10. %o A299777 (PARI) lista(nn) = for (n=1, nn, if (s=sumdiv(n, d, if(d^2>=n/2 && d^2<2*n, d, 0)), print1(s, ", "))); \\ _Michel Marcus_, Apr 24 2018 %Y A299777 Nonzero terms in A071090. %Y A299777 Companion of A281007. %Y A299777 Cf. A071562. %K A299777 nonn %O A299777 1,3 %A A299777 _Omar E. Pol_, Apr 07 2018