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 A080756 #13 Aug 27 2025 06:59:55 %S A080756 8,9,12,16,18,20,24,25,27,28,32,36,40,44,45,48,49,50,52,54,56,60,63, %T A080756 64,68,72,75,76,80,81,84,88,90,92,96,98,99,100,104,108,112,116,117, %U A080756 120,121,124,125,126,128,132,135,136,140,144,147,148,150,152,153,156,160 %N A080756 Numbers k such that there are infinitely many multiples of k that have exactly k divisors. %C A080756 Regional Math Competition for Northwestern Bulgaria, Vraca 2003, Problem 12/3. %C A080756 Sequence consists of all nonsquarefree numbers except for the number 4. %e A080756 8 is a term because all numbers of the form 2^3*p (where p is an odd prime) have exactly 8 divisors and are multiples of 8. %e A080756 Any squarefree number has only a finite number of such multiples. The number 4 has only one such multiple (8). %Y A080756 Essentially the same as A013929. %K A080756 nonn,changed %O A080756 1,1 %A A080756 _Ivaylo Kortezov_, Mar 09 2003 %E A080756 Edited by _Jon E. Schoenfield_, Oct 28 2023