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 A357808 #10 Oct 29 2022 04:42:40 %S A357808 4,6,14,115,118,178,187,214,235,3066899,3067069,3067079,3067149, %T A357808 3067429,3067549,3067594,3067609,3067669,3067719,3067999,44690978147, %U A357808 44690978217,44690978245,44690978623,44690978903,44690979022,44690979442 %N A357808 Semiprimes k such that k is congruent to 4 modulo k's index in the sequence of semiprimes. %C A357808 a(28) > 8040423200947. %C A357808 a(28) <= 1095927464608618, a(29) <= 1095927464608951 and a(38) <= 1095927464630173. - _Martin Ehrenstein_, Oct 28 2022 %H A357808 Lucas A. Brown, <a href="https://github.com/lucasaugustus/oeis/blob/main/semiprimemods.py">semiprimemods.py</a>. %F A357808 a(n) = A001358(A106129(n)). %e A357808 The 1st semiprime is 4, which is congruent to 4 (modulo 1), so 4 is in the sequence. %e A357808 The 2nd semiprime is 6, which is congruent to 4 (modulo 2), so 6 is in the sequence. %e A357808 The 3rd semiprime is 9, which is not congruent to 4 (modulo 3), so 9 is not in the sequence. %e A357808 The 4th semiprime is 10, which is not congruent to 4 (modulo 4), so 10 is not in the sequence. %e A357808 The 5th semiprime is 14, which is congruent to 4 (modulo 5), so 14 is in the sequence. %Y A357808 Cf. A001358, A106129. %K A357808 nonn,hard,more %O A357808 1,1 %A A357808 _Lucas A. Brown_, Oct 13 2022