A360422 Numbers k such that k^2 + (sum of fourth powers of the digits of k^2) is a square.
0, 89, 137, 6985
Offset: 1
Examples
a(3) = 137 is a term because 137^2 = 18769 and 18769 + 1^4 + 8^4 + 7^4 + 6^4 + 9^4 = 182^2.
Programs
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Maple
select(n -> issqr(n^2 + add(t^4, t = convert(n^2,base,10))), [$0..32918]);
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Python
from math import isqrt def sq(n): return isqrt(n)**2 == n def ok(n): return sq(n**2 + sum(int(d)**4 for d in str(n**2))) print([k for k in range(10**5) if ok(k)]) # Michael S. Branicky, Feb 12 2023
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