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A309762
Numbers that are the sum of 3 nonzero 4th powers in more than one way.
10
2673, 6578, 16562, 28593, 35378, 42768, 43218, 54977, 94178, 105248, 106353, 122018, 134162, 137633, 149058, 171138, 177042, 178737, 181202, 195122, 195858, 198497, 216513, 234273, 235298, 235553, 264113, 264992, 300833, 318402, 318882, 324818, 334802, 346673
OFFSET
1,1
LINKS
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 &]
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Aug 15 2019
STATUS
approved