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 A382628 #19 Apr 12 2025 11:57:52
%S A382628 3367,4921,8911,9919,10621,14911,18487,21931,25669,27937,37297,41419,
%T A382628 55081,63511,66157,72541,80197,106597,108871,113491,117019,130417,
%U A382628 134197,136747,139321,174967,195841,198919,203581,219511,226051,232687,236041,244531,247969,256669,258427,269101,272707,287371
%N A382628 Centered hexagonal numbers that are sphenic numbers.
%C A382628 All terms are odd.
%F A382628 a(n) == 1 (mod 6).
%e A382628 3367 is the 33rd centered hexagonal number and 3367 = 7*13*37 is the product of 3 distinct primes.
%e A382628 8911 is the 54th centered hexagonal number and 8911 = 7*19*67 is the product of 3 distinct primes.
%t A382628 Select[Table[3*n*(n+1) + 1, {n, 0, 400}], FactorInteger[#][[;; , 2]] == {1, 1, 1} &] (* _Amiram Eldar_, Apr 01 2025 *)
%o A382628 (PARI) select(x->((omega(x)==3) && (bigomega(x)==3)), vector(100, n, 3*n*(n+1) + 1)) \\ _Michel Marcus_, Apr 02 2025
%Y A382628 Intersection of A007304 and A003215.
%Y A382628 Cf. A113530.
%K A382628 nonn
%O A382628 1,1
%A A382628 _Massimo Kofler_, Apr 01 2025