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 A095739 #16 Feb 16 2025 08:32:53 %S A095739 18,45,48,52,136,148,160,162,176,192,196,208,232,244,261,272,292,296, %T A095739 297,304,320,352,369 %N A095739 Numbers known to be solitary but not coprime to sigma. %C A095739 Abundancy is defined as the ratio of the multiplicative sum-of-divisors function to the integer itself: abund(n) = sigma(n)/n. E.g., abund(10) = sigma(10)/10 = (1+2+5+10)/10 = 1.8 = 9/5. %C A095739 Integers m and n are friendly iff they have the same abundancy. E.g., abund(12) = abund(234) = 7/3 ===> 12 and 234 are friends. %C A095739 Integers which have no friends are called solitary. %C A095739 "It is believed that 10, 14, 15, 20, 22, 26, 33, 34, 38, 44, 46, 51, 54, 58, 62, 68, 69, 70, 72, 74, 76, 82, 86, 87, 88, 90, 91, 92, 94, 95, 99, 104, 105, 106 and many others are also solitary, although a proof appears to be extremely difficult." Quote from _Eric W. Weisstein_. - _Franklin T. Adams-Watters_, Feb 02 2006 %H A095739 Claude W. Anderson and Dean Hickerson, <a href="http://www.jstor.org/stable/2318325">Advanced Problem 6020: Friendly Integers</a>, Amer. Math. Monthly, 1977, V84#1p65-6. %H A095739 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SolitaryNumber.html">Solitary Number.</a> %Y A095739 Cf. A095738, A074902. %K A095739 nonn %O A095739 1,1 %A A095739 _Walter Nissen_, Jul 08 2004 %E A095739 More terms from _Franklin T. Adams-Watters_, Feb 02 2006