A359845 Centered triangular numbers which are products of four distinct primes.

9010, 20710, 39610, 67735, 91885, 108946, 163846, 191710, 197110, 237010, 243010, 293710, 307135, 342010, 349210, 409510, 461206, 466210, 474610, 488206, 526585, 544510, 619210, 625006, 640594, 656374, 678385, 688510, 698710, 708985, 789526, 890506, 934966, 985366, 992674, 1039585

Offset

1,1

Comments

A squarefree subsequence of centered triangular numbers.

Links

Table of n, a(n) for n=1..36.

Example

9010 = 2 * 5 * 17 * 53 = (3 * 78 * (78 - 1) / 2) + 1.
20710 = 2 * 5 * 19 * 109 = (3 * 118 * (118 - 1) / 2) + 1.
39610 = 2 * 5 * 17 * 233 = (3 * 163 * (163 - 1) / 2) + 1.

Mathematica

Select[Table[3*n*(n - 1)/2 + 1, {n, 1, 1000}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* Amiram Eldar, Jan 15 2023 *)

Crossrefs

Intersection of A005448 and A046386.

Sequence in context: A326319 A102484 A295457 * A252456 A196994 A250828

Adjacent sequences: A359842 A359843 A359844 * A359846 A359847 A359848

Keyword

nonn

Author

Massimo Kofler, Jan 15 2023

Status

approved