A368424 Numbers k such that gcd(A019320(k), A019321(k)) > 1.

4, 11, 18, 20, 23, 28, 35, 43, 48, 52, 83, 95, 100, 119, 131, 138, 148, 155, 162, 166, 172, 179, 191, 196, 204, 210, 214, 239, 251, 253, 268, 292, 299, 300, 316, 323, 342, 359, 371, 378, 388, 419, 431, 443, 460, 463, 491, 500, 508, 515, 537, 556, 564, 575

Offset

1,1

Comments

The corresponding greatest common divisors are given in A368425.

Links

Robert Israel, Table of n, a(n) for n = 1..1000

Example

a(1) = 4 since A019320(4) = 5 and A019321(4) = 10.

Maple

select(k -> igcd(numtheory:-cyclotomic(k, 2),
numtheory:-cyclotomic(k, 3)) > 1, [$1..1000]); # Robert Israel, Dec 26 2023

Mathematica

Select[Range[600], GCD[Cyclotomic[#, 2], Cyclotomic[#, 3]]>1&] (* Stefano Spezia, Dec 26 2023 *)

Prog

(PARI) for(n=1, 1000, if(gcd(polcyclo(n, 2), polcyclo(n, 3))>1, print1(n, ", ")))

Crossrefs

Cf. A019320, A019321, A191609 (prime factors of such gcds), A368425.

Sequence in context: A063556 A133725 A050395 * A059771 A325618 A361131

Adjacent sequences: A368421 A368422 A368423 * A368425 A368426 A368427

Keyword

nonn

Author

Tomohiro Yamada, Dec 24 2023

Status

approved