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

Author

Massimo Kofler, Mar 10 2025

Keywords

• nonn

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).
		

Crossrefs

Intersection of A000384 and A046386.

Cf. A129521, A380007.

Programs

Mathematica

Select[Table[n*(2*n-1), {n, 1, 220}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* Amiram Eldar, Mar 10 2025 *)