login
A336403
Multiplicative closure of A045468: numbers which are the product of zero or more primes which are 1 or 4 mod 5.
2
1, 11, 19, 29, 31, 41, 59, 61, 71, 79, 89, 101, 109, 121, 131, 139, 149, 151, 179, 181, 191, 199, 209, 211, 229, 239, 241, 251, 269, 271, 281, 311, 319, 331, 341, 349, 359, 361, 379, 389, 401, 409, 419, 421, 431, 439, 449, 451, 461, 479, 491, 499, 509
OFFSET
1,2
COMMENTS
The subsequence of A089270 which excludes terms divisible by 5.
FORMULA
Numbers of the form r^2 + 3*r*s + s^2 not divisible by 5, where r and s are relatively prime and r > s >= 0.
CROSSREFS
Cf. A031363 and its subset A089270 and its subset A038872 and its subset A045468.
Sequence in context: A158290 A328896 A057538 * A123976 A045468 A196095
KEYWORD
nonn,easy
AUTHOR
David Friend, Jul 20 2020
EXTENSIONS
New name and general cleanup by Charles R Greathouse IV, Sep 09 2022
STATUS
approved