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 A368425 #20 Jan 25 2024 08:06:18 %S A368425 5,23,19,5,47,29,71,431,97,53,167,191,505,239,263,139,149,311,163,499, %T A368425 173,359,383,197,409,211,643,479,503,23,269,293,599,1201,317,647,19, %U A368425 719,743,379,389,839,863,887,461,11113,983,5,509,1031,4297,557,1129 %N A368425 The corresponding greatest common divisors to A368424(n). %H A368425 Robert Israel, <a href="/A368425/b368425.txt">Table of n, a(n) for n = 1..1000</a> %e A368425 a(2) = 23 since gcd(A019320(A368424(2)), A019321(A368424(2))) = gcd(2047, 88573) = 23. %p A368425 subs(1=NULL, [seq(igcd(numtheory:-cyclotomic(n,2), numtheory:-cyclotomic(n,3)),n=1..1000)]); # _Robert Israel_, Dec 26 2023 %t A368425 Select[GCD[Cyclotomic[Range[600], 2], Cyclotomic[Range[600], 3]],#>1&] (* _Stefano Spezia_, Dec 26 2023 *) %o A368425 (PARI) for(n=1,1000,m=gcd(polcyclo(n,2),polcyclo(n,3));if(m>1,print1(m,", "))) %Y A368425 Cf. A019320, A019321, A191609 (primes dividing some term of this sequence), A368424. %K A368425 nonn,look %O A368425 1,1 %A A368425 _Tomohiro Yamada_, Dec 24 2023