OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..1616
Eric Weisstein's World of Mathematics, Biquadratic Number
EXAMPLE
2673 = 2^4 + 4^4 + 7^4 = 3^4 + 6^4 + 6^4, so 2673 is in the sequence.
MAPLE
N:= 10^6: # for terms <= N
V:= Vector(N, datatype=integer[4]):
for a from 1 while a^4 <= N do
for b from 1 to a while a^4+b^4 <= N do
for c from 1 to b do
v:= a^4+b^4+c^4;
if v > N then break fi;
V[v]:= V[v]+1
od od od:
select(i -> V[i]>1, [$1..N]); # Robert Israel, Aug 19 2019
MATHEMATICA
Select[Range@350000, Length@Select[PowersRepresentations[#, 3, 4], ! MemberQ[#, 0] &] > 1 &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Aug 15 2019
STATUS
approved