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

1,2

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

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

Adjacent sequences: A336400 A336401 A336402 * A336404 A336405 A336406

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