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 A200981 #12 Aug 03 2014 14:01:36 %S A200981 3,4,10,21,34,46,58,70,85,93,118,129,130,144,178,201,226,237,262,298, %T A200981 310,322,324,325,333,334,346,382,406,418,430,466,478,502,513,514,517, %U A200981 549,598,622,633,634,657,658,669,706,730,742,813,826,837,838 %N A200981 Numbers n such that the sum of non-divisors of n is prime. %H A200981 Paolo P. Lava, <a href="/A200981/b200981.txt">Table of n, a(n) for n = 1..10000</a> %e A200981 Non-divisors of 10 are 3, 4, 6, 7, 8, 9 and their sum is 37 that is prime. %p A200981 with(numtheory); %p A200981 P:=proc(i) %p A200981 local a,n; %p A200981 for n from 1 to i do %p A200981 a:=n*(n+1)/2-sigma(n); if isprime(a) then print(n); fi; %p A200981 od; %p A200981 end: %p A200981 P(1000000); %t A200981 okQ[n_] := (n > 0) && PrimeQ[n]; Select[Range[1000], okQ[# (#+1)/2 - DivisorSigma[1, #]] &] (* _T. D. Noe_, Dec 15 2011 *) %Y A200981 Cf. A023194, A024816. %K A200981 nonn,easy %O A200981 1,1 %A A200981 _Paolo P. Lava_, Dec 13 2011