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 A283147 #8 Mar 01 2017 17:14:39 %S A283147 1,2,4,9,12,16,25,48,64,112,192,240,289,448,729,960,1344,1681,1984, %T A283147 2401,3481,4096,5041,6720,7921,10201,12288,15625,17161,27889,28561, %U A283147 28672,29929,39270,53130,61440,65536,71610,82110 %N A283147 Number n such that there are no primes of the form sigma(n)/k where 1 < k < n is a (proper) nondivisor of n. %o A283147 (PARI) is(n)=my(s=sigma(n), p=factor(s)[,1], k); for(i=1,#p, k=s/p[i]; if(k<n&&n%k, return(0))); 1 \\ _Charles R Greathouse IV_, Mar 01 2017 %Y A283147 Supersequence of A023194, A019279 and A061652. %Y A283147 Cf. A000203, A173540. %K A283147 nonn %O A283147 1,2 %A A283147 _Juri-Stepan Gerasimov_, Mar 01 2017 %E A283147 Corrected by _Charles R Greathouse IV_, Mar 01 2017