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 A324991 #8 Nov 21 2024 19:51:31 %S A324991 2,4,8,12,0,18,24,21,30,36,40,48,45,60,56,72,63,84,90,75,96,120,108, %T A324991 112,0,144,110,140,0,180,160,156,136,67,116,210,240,200,198,252,175, %U A324991 224,208,225,288,228,0,360,336,0,172,315,0,330,272,420,294,306,0,396 %N A324991 a(n) = the largest number k such that floor(sigma(k)/tau(k)) = n, or 0 if no such number k exists. %C A324991 Floor(sigma(n)/tau(n)) = floor(A000203(n)/A000005(n)) = A057022(n) for n >= 1. %C A324991 a(n) = 0 for numbers n = 5, 25, 29, 47, 50, 53, 59, 83, 89, ... %e A324991 For n = 4; number 12 is the largest number k with floor(sigma(k)/tau(k)) = 4; floor(sigma(12)/tau(12)) = floor(28/6) = 4. %o A324991 (Magma) [Max([n: n in[1..10^5] | Floor(SumOfDivisors(n)/ NumberOfDivisors(n)) eq k]): k in [1..4]] cat [0] cat [Max([n: n in[1..10^5] | Floor(SumOfDivisors(n)/ NumberOfDivisors(n)) eq k]): k in [6..24]]; %Y A324991 Cf. A000005, A000203, A057022, A162538, A324990. %K A324991 nonn %O A324991 1,1 %A A324991 _Jaroslav Krizek_, Mar 23 2019