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 A092021 #13 Nov 16 2023 15:56:50 %S A092021 1,2,3,5,7,10,15,19,22,24,26,27,31,36,41,44,57,60,67,78,84,87,91,93, %T A092021 101,102,103,104,105,107,115,116,120,121,124,126,128,129,131,135,136, %U A092021 137,138,140,151,161,168,183,186,189,190,191,195,208,215,225,227,228,231 %N A092021 Numbers k such that k-th prime + k-th semiprime is semiprime. %H A092021 Robert Israel, <a href="/A092021/b092021.txt">Table of n, a(n) for n = 1..10000</a> %e A092021 3 is a member because third prime is 5, third semiprime is 9 and 5+9=14 is semiprime. %p A092021 P:= select(isprime, [2,seq(i,i=3..10000,2)]): %p A092021 S:= select(t -> numtheory:-bigomega(t)=2, [$4..10000]): %p A092021 select(t -> numtheory:-bigomega(P[t]+S[t]) = 2, [$1 .. min(nops(P), nops(S))]); # _Robert Israel_, Nov 15 2023 %Y A092021 Cf. A092108. %K A092021 easy,nonn %O A092021 1,2 %A A092021 _Ray Chandler_, Feb 24 2004