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 A095751 #25 Oct 09 2023 14:04:45 %S A095751 66,78,102,114,120,132,138,150,174,186,204,222,228,246,252,258,276, %T A095751 282,294,300,308,312,318,330,348,354,364,366,372 %N A095751 Conjectured list of integers known to be friendly but not known to be primitive friendly. %C A095751 There may be other integers in the sequence within the range of those given, but they have yet to be calculated and moreover, some of these given may prove to be primitive friendly. %C A095751 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 A095751 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 A095751 Friends m and n are primitive friendly iff they have no common prime factor of the same multiplicity. %D A095751 Hickerson, Dean; "Re: Friendly number", post to sci.math newsgroup, 2000, available through groups.google.com. %H A095751 Claude W. Anderson and Dean Hickerson, <a href="https://www.jstor.org/stable/2318325">Problem 6020: Friendly Integers</a>, Amer. Math. Monthly 84 (1977) pp. 65-66. %H A095751 Walter Nissen, <a href="https://listserv.nodak.edu/cgi-bin/wa.exe?A2=NMBRTHRY;560ec1b3.0407">Primitive Friendly Integers and Exclusive Multiples</a>, 2004 post to NMBRTHRY mailing list %e A095751 66 is a friend of 308, 5456, 89408 and 369053696, but all of these are divisible by 11 and not 121, while 66 is not known to be primitive friendly. %e A095751 280 is not a term because although 280 = 2^3*5*7 and 1553357978368 = 2^8*7^2*19^2*37*73*127 have the same abundancy they have no common prime factors of the same multiplicity and so are primitive friendly. It should be noted that 18620 = 2^2*5*7^2*19 also has the same abundancy. - _Suyash Pandit_, Sep 24 2023 %Y A095751 Cf. A014567, A074902, A095738, A095739, A096366. %K A095751 nonn,more %O A095751 1,1 %A A095751 _Walter Nissen_, Jul 09 2004 %E A095751 Terms 280 and 360 removed by _Suyash Pandit_, Sep 24 2023 %E A095751 Added "Conjectured" to definition following comments from the Editors. - _N. J. A. Sloane_, Oct 09 2023