A336403 Multiplicative closure of A045468: numbers which are the product of zero or more primes which are 1 or 4 mod 5.

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

Author

David Friend, Jul 20 2020

Keywords

• nonn
• easy

Comments

The subsequence of A089270 which excludes terms divisible by 5.

Links

• David Friend, Table of n, a(n) for n = 1..10000
• David Friend, Fibonacci-Like Sequences and their Cassini Constants, Multiplication and Factorisation

Crossrefs

Cf. A031363 and its subset A089270 and its subset A038872 and its subset A045468.

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.

Extensions

New name and general cleanup by Charles R Greathouse IV, Sep 09 2022