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 A343827 #19 May 26 2021 02:53:37 %S A343827 441,693,1089,1197,1449,1617,1881,1953,2277,2541,2709,2793,2961,3069, %T A343827 3249,3381,3717,3933,4221,4257,4473,4557,4653,4761,4977,5229,5301, %U A343827 5841,5929,6321,6417,6489,6633,6741,6897,6909,7029,7353,7581,7821,8001,8037,8217,8253 %N A343827 Numbers which are the product of two S-primes (A057948) in exactly two ways. %C A343827 First differs from A057950 at a(21)=4473, whereas A057950(21)=4389, which can be represented as the product of two S-primes in exactly 3 ways. %C A343827 There exist numbers which are the product of two S-primes in exactly 1, 2, and 3 ways; however, it is unknown if any numbers exist which are the product of two S-primes in exactly 4 ways. %H A343827 Zachary DeStefano, <a href="/A343827/b343827.txt">Table of n, a(n) for n = 1..2484</a> %F A343827 a(n) == 1 (mod 4). - _Hugo Pfoertner_, May 01 2021 %e A343827 1449=9*161=21*69 which are all S-primes (A057948), and admits no other S-prime factorizations. %o A343827 (PARI) \\ uses is(n) from A057948 %o A343827 isok(n) = sumdiv(n, d, (d<=n/d) && is(d) && is(n/d)) == 2; \\ _Michel Marcus_, May 01 2021 %Y A343827 Cf. A054520, A057948, A057949, A057950. %Y A343827 Exactly one way: A343826. Exactly three ways: A343828. %K A343827 nonn %O A343827 1,1 %A A343827 _Zachary DeStefano_, Apr 30 2021