A354776 Even numbers that are the sum of two squares; also numbers which are twice the sum of two squares.

0, 2, 4, 8, 10, 16, 18, 20, 26, 32, 34, 36, 40, 50, 52, 58, 64, 68, 72, 74, 80, 82, 90, 98, 100, 104, 106, 116, 122, 128, 130, 136, 144, 146, 148, 160, 162, 164, 170, 178, 180, 194, 196, 200, 202, 208, 212, 218, 226, 232, 234, 242, 244, 250, 256, 260, 272, 274, 288, 290, 292, 296, 298, 306, 314, 320

Offset: 1

Author

N. J. A. Sloane, Jun 26 2022, following a suggestion from Charles Kusniec

Keywords

• nonn

Comments

This is both the even subsequence of A001481, and twice A001481. It is an easy exercise to show that these two definitions produce the same sequence.

Crossrefs

Cf. A001481. Essentially the same as A128106.

Programs

Python

from itertools import count, islice
from sympy import factorint
def A354776_gen(): # generator of terms
    return filter(lambda n:(lambda m:all(d & 3 != 3 or m[d] & 1 == 0 for d in m))(factorint(n//2)),count(0,2))
A354776_list = list(islice(A354776_gen(),30)) # Chai Wah Wu, Jun 27 2022