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 A260335 Prime determinants of forms with class number > 2. 1
 79, 223, 359, 439, 443, 499, 659, 727, 839, 1087, 1091, 1171, 1223, 1327, 1367, 1523, 1567, 1627, 1787, 1811, 1847, 1907, 1987, 2027, 2099, 2143, 2207, 2251, 2399, 2459, 2467, 2543, 2659, 2711, 2971, 3023, 3163, 3251, 3391, 3719, 3739, 3803, 3967, 4139, 4159, 4271 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also primes p == 3 (mod 4) such that Z[sqrt(p)] = Z[x]/(x^2 - p) is not a unique factorization domain (or equivalently, not a principal ideal domain). - Jianing Song, Feb 17 2021 LINKS M. Suryanarayana, Positive determinants of binary quadratic forms whose class-number is 2, Proceedings of the Indian Academy of Sciences. Section A, 2 (1935), 178-179. PROG (PARI) isA260335(p) = isprime(p) && (p%4==3) && quadclassunit(4*p)[1] > 1 \\ Jianing Song, Feb 17 2021 CROSSREFS Cf. A002052. Sequence in context: A142198 A089686 A278837 * A257933 A258098 A141964 Adjacent sequences:  A260332 A260333 A260334 * A260336 A260337 A260338 KEYWORD nonn,more AUTHOR N. J. A. Sloane, Jul 27 2015 EXTENSIONS More terms from Jianing Song, Feb 17 2021 STATUS approved

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Last modified January 20 13:25 EST 2022. Contains 350472 sequences. (Running on oeis4.)