This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A354086 #32 Mar 10 2025 14:49:32 %S A354086 4785,8170,11526,14421,27105,30710,38595,59110,60146,77946,94105, %T A354086 107570,118990,120458,121935,132526,140361,141955,156706,158390, %U A354086 161785,181101,199606,203415,213095,215058,217030,221001,243485,249806,267058,287155,298635,303290 %N A354086 11-gonal numbers which are products of four distinct primes. %C A354086 A squarefree subsequence of 11-gonal numbers, i.e., numbers of the form k*(9*k-7)/2. %e A354086 4785 = 33*(9*33-7)/2 = 3*5*11*29. %e A354086 30710 = 83*(9*83-7)/2 = 2*5*37*83. %e A354086 140361 = 177*(9*177-7)/2 = 3*13*59*61. %e A354086 303290 = 260*(9*260-7)/2 = 2*5*13*2333. %p A354086 q:= n-> is(map(x-> x[2], ifactors(n)[2])=[1$4]): %p A354086 select(q, [n*(9*n-7)/2$n=1..300])[]; # _Alois P. Heinz_, Jun 15 2022 %t A354086 Select[Table[n*(9*n - 7)/2, {n, 1, 300}], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} &] (* _Amiram Eldar_, Jun 08 2022 *) %Y A354086 Intersection of A051682 and A046386. %K A354086 nonn %O A354086 1,1 %A A354086 _Massimo Kofler_, Jun 08 2022