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 A339410 #17 Mar 05 2023 09:41:39
%S A339410 1,1,6,2,9,8,6,35,40,54,10,104,54,135,24,209,126,64,70,90,350,405,72,
%T A339410 154,594,190,740,64,819,280,216,330,989,54,1274,504,22,1595,256,550,
%U A339410 1710,640,714,270,2079,874,2345,648,56,2484,90,2925,1144,286,3239,936,1450,3740,1560,216,832,4464
%N A339410 If the n-th semiprime is p*q with p<=q primes, a(n) is the area of the triangle with vertices (1,p), (p,q) and (q,p*q).
%H A339410 Robert Israel, <a href="/A339410/b339410.txt">Table of n, a(n) for n = 1..10000</a>
%F A339410 a(n) = (q-1)*|p^2-q|/2 where p = A084126(n) and q = A084127(n).
%e A339410 For n = 5 the 5th semiprime is 14=2*7, and the area of the triangle with vertices (1,2), (2,7) and (7,14) is a(5)=9.
%p A339410 N:= 1000: # for semiprimes <= N
%p A339410 SP:= select(t -> numtheory:-bigomega(t)=2, [$4..N]):
%p A339410 f:= proc(n) local p,q;
%p A339410 p,q:= (min,max)(numtheory:-factorset(n));
%p A339410 (q-1)*abs(p^2-q)/2
%p A339410 end proc:
%p A339410 map(f, SP);
%t A339410 ar[{a_,b_}]:=Abs[Det[{{1,a,b},{a,b,a b},{1,1,1}}]]/2; ar/@(If[Length[#]==1,Flatten[ {#,#}],#]&/@(FactorInteger[#][[;;,1]]&/@Select[Range[200],PrimeOmega[ #] == 2&])) (* _Harvey P. Dale_, Mar 05 2023 *)
%Y A339410 Cf. A001358, A084126, A084127.
%K A339410 nonn,look
%O A339410 1,3
%A A339410 _J. M. Bergot_ and _Robert Israel_, Dec 03 2020