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 A122488 #15 Nov 03 2022 19:38:48 %S A122488 1,3,4,5,6,8,9,10,11,15,20,21,22,29,30,33,35,36,40,42,45,47,48,50,54, %T A122488 57,59,60,64,66,69,72,75,76,77,78,80,81,82,84,86,89,95,96,100,102,108, %U A122488 110,111,112,113,116,123,125,130,131,132,134,136,143,146,147,148,152,153 %N A122488 Numbers k such that 1 + 2k + 3k^2 is semiprime. %H A122488 Robert Israel, <a href="/A122488/b122488.txt">Table of n, a(n) for n = 1..10000</a> %e A122488 k=3 is a term because 1 + 2k + 3k^2 = 34 = 2*17 (semiprime); %e A122488 k=4 is a term because 1 + 2k + 3k^2 = 57 = 3*19 (semiprime); etc. %p A122488 filter:= n -> numtheory:-bigomega(1+2*n+3*n^2)=2: %p A122488 select(filter, [$1..200]); # _Robert Israel_, Nov 03 2022 %t A122488 Select[Range[160],PrimeOmega[1+2#+3#^2]==2&] (* _Harvey P. Dale_, Aug 22 2011 *) %Y A122488 Cf. A086285 (numbers k such that 1 + 2k + 3k^2 is prime). %K A122488 nonn %O A122488 1,2 %A A122488 _Zak Seidov_, Oct 20 2006