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 A166983 #11 Aug 20 2025 16:43:21
%S A166983 1,2,4,6,6,6,10,11,11,12,14,17,18,16,22,22,23,22,22,26,29,30,31,27,34,
%T A166983 35,32,34,38,39,42,38,46,44,47,46,46,51,48,53,54,48,58,57,57,61,58,62,
%U A166983 65,62,60,70,69,70,73,70,70,76,78,72,81,82,83,80,78,87,86,89,90,91,84
%N A166983 The n-th composite minus the number of its divisors.
%H A166983 Harvey P. Dale, <a href="/A166983/b166983.txt">Table of n, a(n) for n = 1..1000</a>
%F A166983 a(n)=A002808(n)-A000005(A002808(n)) = A002808(n)-A035004(n+1).
%e A166983 a(1)=4-3=1, a(2)=6-4=2, a(3)=8-4=4.
%t A166983 With[{comps=Rest[Complement[Range[100],Prime[Range[PrimePi[100]]]]]}, #-DivisorSigma[0,#]&/@comps] (* _Harvey P. Dale_, Dec 16 2011 *)
%t A166983 #-DivisorSigma[0,#]&/@Select[Range[100],CompositeQ] (* _Harvey P. Dale_, Aug 20 2025 *)
%Y A166983 Cf. A000005, A002808.
%K A166983 nonn
%O A166983 1,2
%A A166983 _Juri-Stepan Gerasimov_, Oct 26 2009
%E A166983 Formula and two entries corrected by _R. J. Mathar_, May 21 2010.