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 A163751 #7 Aug 03 2017 00:01:41
%S A163751 0,3,2,2,2,3,4,4,4,5,6,6,6,7,8,8,9,10,11,12,12,12,13,14,15,16,16,17,
%T A163751 18,18,18,19,20,20,21,22,23,24,24,25,26,27,28,28,28,29,30,31,32,32,33,
%U A163751 34,34,34,35,36,37,38,38,39,40,40,41,42,43,44,44,45,46,47,48,49,50,50,51
%N A163751 a(n) = n-th even nonprime minus n-th nonprime.
%H A163751 G. C. Greubel, <a href="/A163751/b163751.txt">Table of n, a(n) for n = 1..1000</a>
%F A163751 a(n) = (A163300(n) - A141468(n)).
%t A163751 nonPrime[n_Integer] := FixedPoint[n + PrimePi@# &, n + PrimePi@n];
%t A163751 A087156[n_] := Mod[n, DivisorSigma[1, n]]; A141468 := Array[nonPrime, 60, 0]; Table[2*A087156[n] - A141468[[n]], {n, 1, 50}] (* _G. C. Greubel_, Aug 02 2017 *)
%Y A163751 Cf. A141468, A163300.
%K A163751 nonn
%O A163751 1,2
%A A163751 _Juri-Stepan Gerasimov_, Aug 03 2009
%E A163751 Entries checked by _R. J. Mathar_, May 21 2010