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 A357807 #10 Oct 16 2022 03:23:53 %S A357807 4,9,15,111,141,237,27663,27667,3066878,3066893,3067023,3067033, %T A357807 3067073,3067193,3067243,3067273,3067283,3067543,3067598,3067613, %U A357807 3067663,3067798,3067843,3067853,3067913,3067933,3067993,348933171,348933219,348933297 %N A357807 Semiprimes k such that k is congruent to 3 modulo k's index in the sequence of semiprimes. %C A357807 a(48) > 8040423200947. %H A357807 Lucas A. Brown, <a href="/A357807/b357807.txt">Table of n, a(n) for n = 1..47</a> %H A357807 Lucas A. Brown, <a href="https://github.com/lucasaugustus/oeis/blob/main/semiprimemods.py">semiprimemods.py</a> %F A357807 a(n) = A001358(A106128(n)). %e A357807 The 1st semiprime is 4, which is congruent to 3 (mod 1), so 4 is in the sequence. %e A357807 The 2nd semiprime is 6, which is not congruent to 3 (mod 2), so 6 is not in the sequence. %e A357807 The 3rd semiprime is 9, which is congruent to 3 (mod 3), so 9 is in the sequence. %e A357807 The 4th semiprime is 10, which is not congruent to 3 (mod 4), so 10 is not in the sequence. %Y A357807 Cf. A001358, A106128. %K A357807 nonn,hard %O A357807 1,1 %A A357807 _Lucas A. Brown_, Oct 13 2022