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 A249671 #16 Nov 10 2014 17:45:17 %S A249671 1,364,86800,90768,149856,632400,828816,46462800,61987600,148468320, %T A249671 153972000,185684160,187465824,189300384,191659104,193808160, %U A249671 196219296,202460352,204118464,215399520,220116960,221931360,222778080,223382880,228584160,338116680 %N A249671 Integers n such that A249670(n) = n. %C A249671 That is, integers n such that A017665(n)*A017666(n) = n. %e A249671 sigma(364)/364 = 28/13 and 28*13 = 364, so 364 is in the sequence. %t A249671 lista[n_Integer] := Select[Range[n], # == Numerator[DivisorSigma[-1, #]] * Denominator[DivisorSigma[-1, #]] &]; %t A249671 lista[10^6] (* _Michael De Vlieger_, Nov 10 2014 *) %o A249671 (PARI) isok(n) = my(ab = sigma(n)/n); numerator(ab)*denominator(ab) == n; \\ _Michel Marcus_, Nov 04 2014 %Y A249671 Cf. A017665, A017666, A249670. %K A249671 nonn %O A249671 1,2 %A A249671 _Michel Marcus_, Nov 03 2014