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A359845
Centered triangular numbers which are products of four distinct primes.
0
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.
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
KEYWORD
nonn
AUTHOR
Massimo Kofler, Jan 15 2023
STATUS
approved