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 A122492 #21 Nov 04 2023 10:28:33 %S A122492 4,6,9,10,15,21,22,33,35,57,69,77,82,86,95,111,123,134,143,146,161, %T A122492 183,202,203,209,218,219,221,249,262,267,298,299,302,314,321,323,326, %U A122492 329,334,335,339,341,417,422,446,454,471,489,515,543,551,554,562,566,573 %N A122492 Semiprimes k such that 1 + 2k + 3k^2 is also semiprime. %H A122492 Vincenzo Librandi, <a href="/A122492/b122492.txt">Table of n, a(n) for n = 1..3500</a> %e A122492 k = 4 = 2*2 (semiprime) is a term because 1 + 2k + 3k^2 = 57 = 3*19 (semiprime), etc. %t A122492 Select[Range[600],PrimeOmega[#]==PrimeOmega[1+2#+3#^2]==2&] (* _Harvey P. Dale_, Nov 04 2023 *) %o A122492 (Magma) IsSemiprime:=func< n | &+[ k[2]: k in Factorization(n) ] eq 2 >; [ n: n in [2..600] | IsSemiprime(n) and IsSemiprime(1+2*n+3*n^2)]; // _Vincenzo Librandi_, Jan 09 2019 %Y A122492 Cf. A086285 (numbers k such that 1 + 2k + 3k^2 is prime). %K A122492 nonn %O A122492 1,1 %A A122492 _Zak Seidov_, Oct 20 2006