A354086 11-gonal (or hendecagonal) numbers which are products of four distinct primes.

4785, 8170, 11526, 14421, 27105, 30710, 38595, 59110, 60146, 77946, 94105, 107570, 118990, 120458, 121935, 132526, 140361, 141955, 156706, 158390, 161785, 181101, 199606, 203415, 213095, 215058, 217030, 221001, 243485, 249806, 267058, 287155, 298635, 303290

Offset

1,1

Comments

A squarefree subsequence of 11-gonal numbers, i.e., numbers of the form k*(9*k-7)/2.

Links

Table of n, a(n) for n=1..34.

Example

4785 = 33*(9*33-7)/2 = 3*5*11*29.
30710 = 83*(9*83-7)/2 = 2*5*37*83.
140361 = 177*(9*177-7)/2 = 3*13*59*61.
303290 = 260*(9*260-7)/2 = 2*5*13*2333.

Maple

q:= n-> is(map(x-> x[2], ifactors(n)[2])=[1$4]):
select(q, [n*(9*n-7)/2$n=1..300])[];  # Alois P. Heinz, Jun 15 2022

Mathematica

Select[Table[n*(9*n - 7)/2, {n, 1, 300}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* Amiram Eldar, Jun 08 2022 *)

Crossrefs

Intersection of A051682 and A046386.

Sequence in context: A189183 A237095 A138087 * A296812 A251775 A096517

Adjacent sequences: A354083 A354084 A354085 * A354087 A354088 A354089

Keyword

nonn

Author

Massimo Kofler, Jun 08 2022

Status

approved