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

1,1

Comments

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

Links

Table of n, a(n) for n=1..32.

Example

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.

Mathematica

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

Prog

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

Crossrefs

Intersection of A001106 and A046387.

Sequence in context: A083622 A237207 A224423 * A258441 A244150 A229798

Adjacent sequences: A356352 A356353 A356354 * A356356 A356357 A356358

Keyword

nonn

Author

Massimo Kofler, Oct 15 2022

Status

approved