A380892 Hexagonal numbers that are abundant.
66, 120, 276, 378, 630, 780, 1128, 1326, 1540, 1770, 2016, 2556, 2850, 3160, 3486, 3828, 4560, 4950, 5778, 6216, 7140, 7626, 7875, 8646, 9180, 9730, 10296, 10878, 12090, 12720, 14028, 14706, 15400, 16110, 16836, 17955, 18336, 19110, 19900, 20706, 21528, 21945, 23220, 24090, 24976
Offset: 1
Keywords
Examples
66 = 2*3*11 is a term since it is a hexagonal number and less than the sum of its proper divisors 78. 120 = 2^3*3*5 is a term since it is a hexagonal number and less than the sum of its proper divisors 240. 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.
Programs
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Mathematica
Select[Table[n*(2*n-1), {n, 1, 125}], DivisorSigma[-1, #] > 2 &] (* Amiram Eldar, Feb 07 2025 *) -
PARI
select(x->sigma(x)>2*x, vector(150, k, k*(2*k-1))) \\ Michel Marcus, Feb 07 2025
Comments