This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
okQ[n_] := n == 1 || AllTrue[FactorInteger[n][[All, 1]], Mod[#, 4] != 1& ]; A000548 = Select[Range[100], okQ]^2 (* Jean-François Alcover, Feb 09 2016 *)
A000161(25)=#{5^2+0^2,4^2+3^2}=2: a(25)=25+0+16+9=50;
A000161(26)=#{5^2+1^2}=1: a(16)=25+1=26;
A000161(49)=#{7^2+0^2}=1: a(49)=49+0=49;
A000161(50)=#{7^2+1^2,5^2+5^2}=2: a(50)=49+1+25=75;
A000161(2600)=#{50^2+10^2,46^2+22^2,38^2+34^2}=3: a(2600)=2500+100+2116+484+1444+1156=7800;
A000161(2601)=#{51^2+0^2,45^2+24^2}=2: a(2601)=2601+0+12025+576=5202;
A000161(2602)=#{51^2+1^2}=1: a(2602)=2601+1=2602.
a(n) = sum(k=1, n, if (issquare(k) && issquare(n-k), k)); \\ Michel Marcus, May 16 2023
from sympy import divisors from sympy.solvers.diophantine.diophantine import cornacchia def A143574(n): c = 0 for d in divisors(n): if (k:=d**2)>n: break q, r = divmod(n,k) if not r: c += sum(k*(a[0]**2+(a[1]**2 if a[0]!=a[1] else 0)) for a in cornacchia(1,1,q) or []) return c # Chai Wah Wu, May 15 2023
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