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 A211658 #17 Dec 20 2021 02:37:33 %S A211658 1,4,8,9,12,18,22,27,32,36,45,49,50,64,72,81,91,98,100,106,121,128, %T A211658 129,133,134,146,148,152,162,169,171,192,200,202,217,218,219,243,256, %U A211658 259,262,268,274,288,289,292,301,314,324,333,338,343,361,381,386,388 %N A211658 Nonprime numbers k such that value of sigma(k) is unique; sigma(k) = A000203(k) = sum of divisors of k. %C A211658 Complement of A066076 with respect to A211656. %H A211658 Amiram Eldar, <a href="/A211658/b211658.txt">Table of n, a(n) for n = 1..10000</a> %e A211658 Number 36 is in the sequence because sigma(36) = 91 and there is no other number m with sigma(m) = 91. %e A211658 Number 6 is not in the sequence because sigma(6) = 12 and 12 is also sigma(11). %Y A211658 Cf. A000203, A066076, A211656, A211657, A211659, A211660. %K A211658 nonn %O A211658 1,2 %A A211658 _Jaroslav Krizek_, Apr 20 2012