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A180161 Numbers that are the sum of two nonnegative squares but are not perfect powers. 0
2, 5, 10, 13, 17, 18, 20, 26, 29, 34, 37, 40, 41, 45, 50, 52, 53, 58, 61, 65, 68, 72, 73, 74, 80, 82, 85, 89, 90, 97, 98, 101, 104, 106, 109, 113, 116, 117, 122, 130, 136, 137, 145, 146, 148, 149, 153, 157, 160, 162, 164, 170, 173, 178, 180, 181, 185, 193, 194, 197, 200, 202, 205, 208, 212, 218, 221, 226, 229, 232, 233 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Terms in A001481 but not in A001597.
LINKS
FORMULA
Numbers of the form 2^i * S^j * T^(2*k) where S is a product of primes 4k+1, T a product of primes 4k+3, i,j,k>=0, and the gcd of the numbers {i, j, 2*k} is 1.
PROG
(PARI)
isA001481(n) =
{
local(x=0, r=0);
while(x<=sqrt(n)&r==0, if(issquare(n-x^2), r=1); x++);
return(r);
}
for(n=2, 1000, if( isA001481(n) && !ispower(n), print1(n, ", ") ) );
CROSSREFS
A001481 (sums of 2 nonnegative squares), A001597 (perfect powers).
Sequence in context: A046462 A188025 A187949 * A349243 A099261 A103215
KEYWORD
nonn
AUTHOR
Joerg Arndt, Jan 16 2011
STATUS
approved

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Last modified March 29 04:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)