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 A152992 #10 May 18 2019 02:05:24
%S A152992 0,0,0,2,1,5,2,7,6,10,5,17,6,14,14,20,9,26,10,28,20,24,13,43,19,29,27,
%T A152992 41,18,54,19,46,33,39,33,71,24,44,40,70,27,75,28,64,58,54,31,99,39,72,
%U A152992 53,77,36,96,52,96,60,70,41,139,42,74,80,102,62,118,47,101,73,117,50
%N A152992 a(n) = sigma(n) - d(n) - pi(n).
%H A152992 Harvey P. Dale, <a href="/A152992/b152992.txt">Table of n, a(n) for n = 1..1000</a>
%F A152992 a(n) = A000203(n) - A000005(n) - A000720(n) = A065608(n) - A000720(n) = A152991(n) - A000005(n).
%e A152992 a(15) = 24 - 4 - 6 = 14 because the sum of divisors of 15 is 1 + 3 + 5 + 15 = 24, the number of divisors of 15 is 4 (1,3,5,15) and the number of primes not exceeding 15 is 6 (2,3,5,7,11,13). - _Emeric Deutsch_, Dec 30 2008
%p A152992 with(numtheory): seq(sigma(n)-tau(n)-pi(n), n = 1 .. 75); # _Emeric Deutsch_, Dec 30 2008
%t A152992 Table[DivisorSigma[1,n]-DivisorSigma[0,n]-PrimePi[n],{n,75}] (* _Harvey P. Dale_, Sep 19 2011 *)
%Y A152992 Cf. A000005, A000203, A000720, A065608, A152770, A152991.
%K A152992 easy,nonn
%O A152992 1,4
%A A152992 _Omar E. Pol_, Dec 19 2008, Dec 31 2008
%E A152992 Corrected and extended by _Emeric Deutsch_, Dec 30 2008