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 A380892 #19 Feb 24 2025 21:22:40
%S A380892 66,120,276,378,630,780,1128,1326,1540,1770,2016,2556,2850,3160,3486,
%T A380892 3828,4560,4950,5778,6216,7140,7626,7875,8646,9180,9730,10296,10878,
%U A380892 12090,12720,14028,14706,15400,16110,16836,17955,18336,19110,19900,20706,21528,21945,23220,24090,24976
%N A380892 Hexagonal numbers that are abundant.
%C A380892 The least term that is coprime to 6 is a(30415179) = 9820742934657655. - _Amiram Eldar_, Feb 07 2025
%e A380892 66 = 2*3*11 is a term since it is a hexagonal number and less than the sum of its proper divisors 78.
%e A380892 120 = 2^3*3*5 is a term since it is a hexagonal number and less than the sum of its proper divisors 240.
%e A380892 7875 = 3^2*5^3*7 is a term since it is a hexagonal number and less than the sum of its proper divisors 8349.
%t A380892 Select[Table[n*(2*n-1), {n, 1, 125}], DivisorSigma[-1, #] > 2 &] (* _Amiram Eldar_, Feb 07 2025 *)
%o A380892 (PARI) select(x->sigma(x)>2*x, vector(150, k, k*(2*k-1))) \\ _Michel Marcus_, Feb 07 2025
%Y A380892 Intersection of A000384 and A005101.
%Y A380892 Cf. A074315, A063734, A117794, A379264.
%K A380892 nonn
%O A380892 1,1
%A A380892 _Massimo Kofler_, Feb 07 2025