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.
a(2) = 325 = 1^2 + 18^2 = 6^2 + 17^2 = 10^2 + 15^2. a(3) = 87539319 = 167^3 + 436^3 = 228^3 + 423^3 = 255^3 + 414^3.
16 = 3 + 13 = 5 + 11. 410 = 7^2 + 19^2 = 11^2 + 17^2. 6058655748 = 61^3 + 1823^3 = 1049^3 + 1699^3. 3262811042 = 7^4 + 239^4 = 157^4 + 227^4.
f:= proc(n) local S,P,p,pn,b;
S:= {}:
P:= {}:
p:= 1:
b:= infinity;
do
p:= nextprime(p);
pn:= p^n;
if pn > b then return b fi;
V:= select(`<`,map(`+`,P,pn),b);
newv:= V intersect S;
S:= S union V;
P:= P union {p^n};
if newv <> {} then
b:= min(newv);
S:= select(`<`,S,b);
P:= select(`<`,P, b);
fi;
od:
end proc:
map(f, [$1..4]); # Robert Israel, Nov 13 2020
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