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 A194263 #29 Mar 17 2020 21:17:17 %S A194263 1729,13981,88537,51319,137149,548497,285541,3372529,18326641,1152271, %T A194263 1809641,3828001,4814857,4797703,79230049,4413223,4209661,19703611, %U A194263 3882139,50357677,70611161,26536591,175493677,85409941,12932989,84350561,192754871,59756863 %N A194263 Numbers that occur more than once in A193873, in order of appearance. %C A194263 Note that a(1) = 1729 is known as the Hardy-Ramanujan number (see A001235). %C A194263 Apparently these numbers occur only twice in A193873. %C A194263 Many of these numbers occur more than twice. For example, 812405017 occurs 3 times, a(67), a(134), and a(268). _Robert Price_, Mar 17 2020 %H A194263 Robert Price, <a href="/A194263/b194263.txt">Table of n, a(n) for n = 1..2554</a> %F A194263 It appears that a(n) = A193873(2*n+1). %F A194263 This conjecture only holds for n<62: a(62)=A193873(124)=A193873(2n)=620378449 %F A194263 , a(63)=A193873(125)=A193873(2n-1)=424315751 %F A194263 . _Robert Price_, Mar 17 2020 %e A194263 1729 is in the sequence because the Hardy-Ramanujan number is also the smallest product of three distinct primes of the form 3*k+1 and also of the form 6*k+1, so 1729 occurs more than once in A193873. %Y A194263 Cf. A001235, A154729, A193869, A193873. %K A194263 nonn %O A194263 1,1 %A A194263 _Omar E. Pol_, Sep 02 2011