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Power equation (Posted on 2025-02-05) Difficulty: 3 of 5
How many ordered triples (a, b, n) of positive integers would satisfy the equation a2 + b4 = 5n?

No Solution Yet Submitted by Danish Ahmed Khan    
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Some Thoughts Computer findings | Comment 1 of 3
I found 6:
a b n
2 1 1
3 2 2
50 5 5
75 10 6
1250 25 9
1875 50 10

2 1 1          4+1=5
3 2 2          9+16=25
50 5 5        2500+625=3125
75 10 6       5625+10000=15625
1250 25 9   1562500+390625=1953125
1875 50 10 3515625+6250000=9765625

-----------
import math
big = 10000

squares = [i**2 for i in range(1,big)]
fourths = [i**4 for i in range(1,big)]
maxsum = squares[-1] + fourths[-1]

toppowerof5 = int(math.log(maxsum,5)) + 1
fifths = [5**i for i in range(1,toppowerof5+1)]

for ax in squares:
    for bx in fourths:
        for nx in fifths:
            if ax + bx == nx:
                print(squares.index(ax)+1,
                      fourths.index(bx)+1,
                      fifths.index(nx)+1)

  Posted by Larry on 2025-02-05 13:51:17
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