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 A230605 #21 Feb 23 2014 07:22:03 %S A230605 4,18,20,24,432,588,692945344 %N A230605 Composite numbers n such that number of non-divisors of n divides sum of non-divisors of n. %C A230605 a(7) > 10^5. %C A230605 Composite numbers n such that A231167(n) mod A049820(n) = 0. Complement of primes (A000040) with respect to A140826. Intersection of A002808 and A140826. %C A230605 The terms 20 and 432 are the only composite numbers < 10^5 that are also terms of A023883. %C A230605 No more terms up to 10^8. - _Michel Marcus_, Nov 09 2013 %C A230605 a(8) > 10^11. - _Donovan Johnson_, Nov 12 2013 %C A230605 a(8) > 4*10^12. - _Giovanni Resta_, Feb 11 2014 %e A230605 20 is in sequence because A024816(20) mod A049820(20) = 168 mod 14 = 0. %o A230605 (PARI) isok(n) = (nnd = n - numdiv(n)) && !isprime(n) && !((n*(n+1)/2-sigma(n)) % nnd); \\ _Michel Marcus_, Nov 09 2013 %Y A230605 Cf. A231167, A000040, A049820, A024816. %K A230605 nonn %O A230605 1,1 %A A230605 _Jaroslav Krizek_, Nov 07 2013 %E A230605 a(7) from _Donovan Johnson_, Nov 10 2013