A381920 Hexagonal numbers that are products of exactly four distinct primes.
1326, 1770, 2145, 2415, 3003, 3486, 4186, 5565, 6670, 7626, 8385, 8646, 9730, 13695, 17205, 17578, 24531, 25878, 27730, 28203, 35245, 35778, 37401, 42486, 47278, 47895, 51681, 59685, 60378, 63190, 63903, 66795, 72010, 74305, 75855, 81406, 84666, 87153, 91378, 95703
Offset: 1
Keywords
Examples
1326 = 2*3*13*17 is the product of 4 distinct primes and the 26th hexagonal number hex(26) = 26(2*26-1). 1770 = 2*3*5*59 is the product of 4 distinct primes and the 30th hexagonal number hex(30) = 30(2*30-1). 2145 = 3*5*11*13 is the product of 4 distinct primes and the 33rd hexagonal number hex(33) = 33(2*33-1).
Programs
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Mathematica
Select[Table[n*(2*n-1), {n, 1, 220}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* Amiram Eldar, Mar 10 2025 *)