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A323272 Numbers of the form p_1*p_2*p_3*...*p_r where r is 2 or an odd number > 2, and the p_i are distinct primes congruent to 1 mod 4 such that Legendre(p_i/p_j) = -1 for all i != j. 4
65, 85, 185, 265, 365, 481, 485, 493, 533, 565, 629, 685, 697, 785, 865, 949, 965, 985, 1037, 1073, 1157, 1165, 1189, 1241, 1261, 1285, 1385, 1417, 1465, 1565, 1585, 1649, 1685, 1765, 1769, 1781, 1853, 1865, 1921, 1937, 1985, 2117, 2165, 2173 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If k is a term, the Pell equation x^2 - k*y^2 = -1 has a solution [Dirichlet, Newman (1977)]. This is only a sufficient condition, there are many other solutions, see A031396.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..10000

Morris Newman, A note on an equation related to the Pell equation, The American Mathematical Monthly 84.5 (1977): 365-366.

CROSSREFS

Cf. A002144, A031396. Includes the union of A322781 and A323271.

Sequence in context: A274044 A024409 A131574 * A322781 A020273 A034071

Adjacent sequences:  A323269 A323270 A323271 * A323273 A323274 A323275

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jan 11 2019

STATUS

approved

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Last modified November 19 03:48 EST 2019. Contains 329310 sequences. (Running on oeis4.)