cp's OEIS Frontend

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

%I A354776 #14 Jul 09 2025 04:59:09
%S A354776 0,2,4,8,10,16,18,20,26,32,34,36,40,50,52,58,64,68,72,74,80,82,90,98,
%T A354776 100,104,106,116,122,128,130,136,144,146,148,160,162,164,170,178,180,
%U A354776 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
%N A354776 Even numbers that are the sum of two squares; also numbers which are twice the sum of two squares.
%C A354776 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.
%o A354776 (Python)
%o A354776 from itertools import count, islice
%o A354776 from sympy import factorint
%o A354776 def A354776_gen(): # generator of terms
%o A354776     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))
%o A354776 A354776_list = list(islice(A354776_gen(),30)) # _Chai Wah Wu_, Jun 27 2022
%Y A354776 Cf. A001481. Essentially the same as A128106.
%K A354776 nonn
%O A354776 1,2
%A A354776 _N. J. A. Sloane_, Jun 26 2022, following a suggestion from _Charles Kusniec_