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

1,2

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.

Links

Table of n, a(n) for n=1..66.

Prog

(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

Crossrefs

Cf. A001481. Essentially the same as A128106.

Sequence in context: A171757 A350780 A128106 * A125021 A085406 A022340

Adjacent sequences: A354773 A354774 A354775 * A354777 A354778 A354779

Keyword

nonn

Author

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

Status

approved