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 A343828 #35 Dec 30 2021 14:36:58 %S A343828 4389,5313,7161,9177,9933,10857,12369,13629,14421,14973,15477,16401, %T A343828 17157,18249,18753,19173,19437,20769,22701,23529,23541,23793,24717, %U A343828 26733,26961,27993,28329,28497,29337,29469,30261,30597,31521,32109,32361,32637,33117,33649 %N A343828 Numbers which are the product of two S-primes (A057948) in exactly three ways. %C A343828 There exist numbers which are the product of two S-primes in exactly 1, 2, and 3 ways. %C A343828 An S-prime is either a prime of the form 4k+1 or a semiprime of the form (4k+3)*(4m+3). That means the maximum number of prime factors that a number factorizable into two S-primes can have is four (all 4k + 3), and those can be combined into S-primes in at most three distinct ways. - _Gleb Ivanov_, Dec 07 2021 %H A343828 Zachary DeStefano, <a href="/A343828/b343828.txt">Table of n, a(n) for n = 1..1014</a> %F A343828 a(n) == 1 (mod 4). - _Hugo Pfoertner_, May 01 2021 %e A343828 9177 = 21*437 = 57*161 = 69*133 which are all S-primes (A057948), and admits no other S-Prime factorizations. %e A343828 4389 = (3*7)*(11*19) = (3*11)*(7*19) = (3*19)*(7*11); 3,7,11,19 are the smallest primes of the form 4k + 3. %o A343828 (PARI) \\ uses is(n) from A057948 %o A343828 isok(n) = sumdiv(n, d, (d<=n/d) && is(d) && is(n/d)) == 3; \\ _Michel Marcus_, May 01 2021 %Y A343828 Cf. A054520, A057948, A057949, A057950. %Y A343828 Exactly one way: A343826. Exactly two ways: A343827. %K A343828 nonn %O A343828 1,1 %A A343828 _Zachary DeStefano_, Apr 30 2021