A356355 9-gonal numbers which are products of five distinct primes.

24486, 71214, 90321, 116754, 123234, 156774, 181374, 265926, 287574, 445179, 450186, 483414, 488631, 595959, 688866, 698214, 781869, 791826, 845994, 912646, 937839, 970734, 1030614, 1042041, 1100121, 1266909, 1463514, 1659801, 2014386, 2041026, 2171334, 2187906

Offset: 1

Author

Massimo Kofler, Oct 15 2022

Keywords

• nonn

Comments

A squarefree subsequence of 9-gonal numbers a(n) = n*(7*n-5)/2.

Examples

			24486 = 2*3*7*11*53 = 84*(7*84-5)/2.
445179 = 3*7*17*29*43 = 357*(7*357-5)/2.
781869 = 3*11*19*29*43 = 473*(7*473-5)/2.
1030614 = 2*3*13*73*181 = 543*(7*543-5)/2.
		

Crossrefs

Intersection of A001106 and A046387.

Programs

Mathematica

Select[Table[n*(7*n - 5)/2, {n, 1, 1000}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1, 1} &] (* Amiram Eldar, Oct 15 2022 *)

PARI

select(x->omega(x)==5&&bigomega(x)==5, vector(800, k, k*(7*k-5)/2)) \\ Michel Marcus, Nov 26 2022