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A159008
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Positive numbers k such that k^2 == 2 (mod 89).
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5
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25, 64, 114, 153, 203, 242, 292, 331, 381, 420, 470, 509, 559, 598, 648, 687, 737, 776, 826, 865, 915, 954, 1004, 1043, 1093, 1132, 1182, 1221, 1271, 1310, 1360, 1399, 1449, 1488, 1538, 1577, 1627, 1666, 1716, 1755, 1805, 1844, 1894, 1933, 1983, 2022, 2072
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OFFSET
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1,1
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COMMENTS
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Numbers congruent to {25, 64} mod 89. - Amiram Eldar, Feb 26 2023
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LINKS
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FORMULA
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a(n) = a(n-1) + a(n-2) - a(n-3).
G.f.: x*(25 + 39*x + 25*x^2)/((1+x)*(x-1)^2).
a(n) = (89 + 11*(-1)^(n-1) + 178*(n-1))/4.
Sum_{n>=1} (-1)^(n+1)/a(n) = tan(39*Pi/178)*Pi/89. - Amiram Eldar, Feb 26 2023
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MATHEMATICA
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Select[Range[2100], PowerMod[#, 2, 89]==2&] (* Harvey P. Dale, May 09 2019 *)
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PROG
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(Magma) I:=[25, 64, 114]; [n le 3 select I[n] else Self(n-1)+Self(n-2)-Self(n-3): n in [1..60]]; // Vincenzo Librandi, Mar 02 2012
(PARI) for(n=1, 60, print1((89+11*(-1)^(n-1)+178*(n-1))/4", ")); \\ Vincenzo Librandi, Mar 02 2012
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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