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 A308169 #10 May 15 2019 13:58:02 %S A308169 3,7,10,11,16,19,22,23,25,27,31,34,43,46,49,58,59,71,79,82,83,94,100, %T A308169 103,106,118,121,131,139,142,163,166,178,191,199,202,208,211,214,223, %U A308169 226,251,262,271,274,298,311,331,334,346,358,359,379,382,383,394,419,443,454,463,466,478,479,484 %N A308169 Numbers k such that A023896(k) mod A000203(k) is prime. %C A308169 Numbers k such that (k*A000010(k)/2) mod A000203(k) is prime. %C A308169 The primes in the sequence are A092109. %C A308169 The even semiprimes in the sequence are A112774. %H A308169 Robert Israel, <a href="/A308169/b308169.txt">Table of n, a(n) for n = 1..10000</a> %e A308169 a(3)=10 is in the sequence because A023896(10) mod A000203(10) = 20 mod 6 = 2, and 2 is prime. %p A308169 select(n -> isprime((n*numtheory:-phi(n)/2) mod numtheory:-sigma(n)), [$2..1000]); %o A308169 (PARI) isok(n) = isprime(n*eulerphi(n)/2 % sigma(n)); \\ _Michel Marcus_, May 15 2019 %Y A308169 Cf. A000010, A000203, A023896, A092109, A112774. %K A308169 nonn %O A308169 1,1 %A A308169 _J. M. Bergot_ and _Robert Israel_, May 15 2019