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A167437
Positive integers c such that c^2 = a + b and a^2 + b^2 = m^4 for some coprime integers a, b, m.
3
1, 1343, 2372159, 9788425919, 5705771236038721, 17999572487701067948161, 173658539553825212149513251457, 75727152767742719949099952561135816319, 437825148963391521638828389137484882137402791039
OFFSET
1,2
COMMENTS
Corresponding values of m are given in A166929 - see it for further details.
Terms with positive a, b are given in A167438.
This is the absolute value of a bisection of a generalized Somos-5 sequence. - Michael Somos, Nov 04 2022
PROG
(PARI) {a(n) = local(x, v); n = abs(2*n+1); (x = m-> v[abs(m)+1]); v = vector(max(3, n+1), m, 1); v[3] = -3; for(k=3, n, v[k+1] = -(13*x(k-1)*x(k-4) + 42*x(k-2)*x(k-3)) / x(k-5)); abs(x(n))}; /* Michael Somos, Nov 04 2022 */
CROSSREFS
Sequence in context: A253114 A237506 A264385 * A259675 A205820 A202430
KEYWORD
nonn
AUTHOR
Max Alekseyev, Nov 03 2009
STATUS
approved