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 A056996 #21 Dec 02 2016 01:11:03
%S A056996 5,11,19,21,23,27,33,35,39,43,45,47,51,53,55,59,67,69,71,79,81,83,87,
%T A056996 95,99,101,103,105,107,113,115,117,119,123,129,131,135,139,141,143,
%U A056996 147,151,153,155,159,165,167,171,173,175,177,179,185,187,189,191,193,195
%N A056996 Positive integers not of the form sigma(k) + phi(k) - 2k for some k.
%C A056996 Under the assumption that every even integer >= 18 is the sum of three distinct primes, all elements of this sequence are odd. See A278373 for more details.
%H A056996 David W. Wilson, <a href="/A056996/b056996.txt">Table of n, a(n) for n = 1..10000</a>
%t A056996 Take[#, 59] &@ Complement[Range@ #, Union@ Table[DivisorSigma[1, n] + EulerPhi@ n - 2 n, {n, #}]] &[10^5] (* _Michael De Vlieger_, Nov 30 2016 *)
%Y A056996 Complement is A278373.
%Y A056996 Cf. A000010 (phi), A000203 (sigma).
%K A056996 nonn
%O A056996 1,1
%A A056996 _David W. Wilson_, Sep 06 2000