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 A375390 #16 Aug 17 2024 14:20:11 %S A375390 44,102,104,108,152,188,226,234,296,328,426,526,586,692,720,842,846, %T A375390 856,926,994,1076,1278,1284,1386,1426,1484,1498,1574,1704,1746,1764, %U A375390 1822,1826,1848,1952,2058,2114,2128,2142,2148,2164,2186,2386,2416,2442,2484,2640,2704,2904,2948,3108,3142,3164 %N A375390 Numbers k such that k^2 + 1, k^2 + 3 and k^2 + 5 are semiprimes. %C A375390 All terms are even. %C A375390 a(n)^2 + 3 or a(n)^2 + 5 is 3 times a prime. In the first case, a(n)/3 is in A111051. %H A375390 Robert Israel, <a href="/A375390/b375390.txt">Table of n, a(n) for n = 1..10000</a> %e A375390 a(3) = 104 is a term because 104^2 + 1 = 10817 = 29 * 373, 104^2 + 3 = 10819 = 31 * 349 and 104^2 + 5 = 10821 = 3 * 3607 are all semiprimes. %p A375390 select(t -> andmap(s -> numtheory:-bigomega(t^2+s)=2, [1,3,5]), 2*[$1..2000]); %t A375390 Select[Range[3000], 2 == PrimeOmega[1 + #^2] == PrimeOmega[3 + %t A375390 #^2] == PrimeOmega [5 + #^2] &] %Y A375390 Cf. A001358, A111051. Intersection of A085722, A242331 and A242333. %K A375390 nonn %O A375390 1,1 %A A375390 _Zak Seidov_ and _Robert Israel_, Aug 15 2024