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 A152864 #7 Apr 07 2024 09:09:30
%S A152864 1,2,3,3,5,3,7,4,7,5,11,1,13,7,9,5,17,2,19,3,13,11,23,-5,21,13,17,5,
%T A152864 29,-5,31,6,21,17,25,-11,37,19,25,-3,41,-5,43,9,17,23,47,-19,43,12,33,
%U A152864 11,53,-5,41,-1,37,29,59,-37,61,31
%N A152864 Deficiency of n, plus the number of proper divisors of n: a(n) = 2n - sigma(n) + d(n) - 1.
%H A152864 Amiram Eldar, <a href="/A152864/b152864.txt">Table of n, a(n) for n = 1..10000</a>
%F A152864 a(n) = A005843(n)-A000203(n)+A000005(n)-1 = A033879(n)+A032741(n).
%t A152864 a[n_] := 2*n - Differences[DivisorSigma[{0, 1}, n]][[1]] - 1; Array[a, 100] (* _Amiram Eldar_, Apr 07 2024 *)
%o A152864 (PARI) a(n) = 2*n - sigma(n) + numdiv(n) - 1; \\ _Amiram Eldar_, Apr 07 2024
%Y A152864 Cf. A000005, A000203, A005843, A032741, A033879, A152770, A152771, A152772.
%K A152864 easy,sign
%O A152864 1,2
%A A152864 _Omar E. Pol_, Dec 14 2008