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 A103655 #10 Sep 08 2024 15:19:52 %S A103655 3,16,19,24,30,32,40,47,54,62,63,68,75,80,87,93,94,95,115,124,126,129, %T A103655 133,136,138,157,160,162,167,169,175,177,179,187,196,205,222,232,233, %U A103655 239,240,247,258,265,267,270,274,277,279,298,299,318,327,335,336,339 %N A103655 Indices of primes which are the average of two successive semiprimes. %H A103655 Zak Seidov, <a href="/A103655/b103655.txt">Table of n, a(n) for n = 1..10000</a> %F A103655 a(n)=pi(A103654(n)). %e A103655 19 is a member because p(19)=67; 65 and 69 are two successive semiprimes closest to 67 and 67=(65+69)/2. %t A103655 PrimePi[#]&/@Select[Mean/@Partition[Select[Range[2500],PrimeOmega[#]==2&],2,1],PrimeQ] (* _Harvey P. Dale_, Sep 08 2024 *) %Y A103655 Corresponding primes: A103654. Primes: A000040, semiprimes: A001358, number of primes between two successive semiprimes: A088700, number of semiprimes between two successive primes: A103668. %Y A103655 Cf. A000040, A088700, A103654, A001358, A103668, A103669. %K A103655 nonn %O A103655 1,1 %A A103655 _Zak Seidov_, Feb 12 2005