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 A227068 #44 Jan 06 2025 21:52:45 %S A227068 2,6,12,24,48,60,144,120,180,240,3072,360,900,960,720,840,5184,1260, %T A227068 36864,1680,2880,3600,12582912,2520,6480,61440,6300,6720,805306368, %U A227068 5040,14400,7560,46080,983040,25920,10080,32400,746496,184320,15120 %N A227068 Least number with exactly n divisors less than its square root. %C A227068 This is similar to A038549, which counts divisors of n <= sqrt(n). Note that an upper bound on a(n) is 3*2^(n-1), which is attained at n = 2, 3, 4, 5, 11, 23, and 29 -- the number 4 and the primes in A005384 (Sophie Germain primes, p and 2p+1 are prime). %C A227068 A056924(a(n)) = n and A056924(m) <> n for m < a(n). - _Reinhard Zumkeller_, Jul 12 2013 %H A227068 Paul Tek, <a href="/A227068/a227068_1.txt">C program for this sequence</a> %e A227068 The divisors of 60 are 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60. Only 6 of these are < sqrt(60). And 60 is the first such number. %t A227068 nn = 22; t = Table[0, {nn}]; found = 0; n = 0; While[found < nn, n++; c = Length[Select[Divisors[n], # < Sqrt[n] &]]; If[c > 0 && c <= nn && t[[c]] == 0, t[[c]] = n; found++]]; t %t A227068 Map[Function[k, FirstPosition[#, k]], Range@ 22] &@ Table[Count[Divisors@ n, m_ /; m < Sqrt@ n], {n, 10^5}] // Flatten (* _Michael De Vlieger_, May 13 2016, Version 10 *) %o A227068 (Haskell) %o A227068 import Data.List (elemIndex); import Data.Maybe (fromJust) %o A227068 a227068 = (+ 1) . fromJust . (`elemIndex` a056924_list) %o A227068 -- _Reinhard Zumkeller_, Jul 12 2013 %o A227068 (C) /* See Tek link. */ %Y A227068 Cf. A005384, A038549, A056924. %K A227068 nonn %O A227068 1,1 %A A227068 _T. D. Noe_, Jul 11 2013 %E A227068 a(29) from _Paul Tek_, Jul 13 2013