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 A137945 #12 Feb 16 2025 08:33:07
%S A137945 36,100,120,144,168,196,225,264,270,280,312,324,378,400,408,440,441,
%T A137945 456,484,520,552,576,594,616,676,680,696,702,728,744,750,760,784,888,
%U A137945 918,920,945,952,960,984,1026,1032,1064,1089,1128,1144,1156,1160,1225,1240
%N A137945 Non-prime-powers such that the number of composite divisors is a multiple of the number of prime divisors.
%H A137945 Amiram Eldar, <a href="/A137945/b137945.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Reinhard Zumkeller)
%H A137945 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DivisorFunction.html">Divisor Function</a>
%F A137945 A055212(a(n)) mod A001221(a(n)) = 0.
%e A137945 A055212(120) = #{4,6,8,10,12,15,20,24,30,40,60,120} = 12 = 4*A001221(120) = 4*#{2,3,5} = 12, therefore 120 is a term.
%t A137945 aQ[n_] := (omega = PrimeNu[n]) > 1 && Divisible[DivisorSigma[0, n] - 1, omega]; Select[Range[2, 1240], aQ] (* _Amiram Eldar_, Aug 31 2019 *)
%Y A137945 Cf. A001221, A055212.
%Y A137945 Intersection of A024619 and A137944.
%K A137945 nonn
%O A137945 1,1
%A A137945 _Reinhard Zumkeller_, Feb 24 2008