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A056082
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Numbers k such that k^4 == 1 (mod 5^3).
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8
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1, 57, 68, 124, 126, 182, 193, 249, 251, 307, 318, 374, 376, 432, 443, 499, 501, 557, 568, 624, 626, 682, 693, 749, 751, 807, 818, 874, 876, 932, 943, 999, 1001, 1057, 1068, 1124, 1126, 1182, 1193, 1249, 1251, 1307, 1318, 1374, 1376, 1432, 1443, 1499, 1501
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OFFSET
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1,2
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COMMENTS
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Numbers that are congruent to {1, 57, 68, 124} mod 125.
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LINKS
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FORMULA
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G.f.: x*(1+56*x+11*x^2+56*x^3+x^4)/((x-1)^2*(1+x+x^2+x^3)).
a(n) = a(n-1) + a(n-4) - a(n-5) for n>5.
a(n) = (250*n-125+99*i^(2*n)+(9-9*i)*i^(-n)+(9+9*i)*i^n)/8 where i=sqrt(-1). (End)
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MAPLE
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MATHEMATICA
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x=5; Select[ Range[ 1000 ], PowerMod[ #, x-1, x^3 ]==1& ]
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PROG
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(Magma) [n : n in [0..2000] | n mod 125 in [1, 57, 68, 124]]; // Wesley Ivan Hurt, Jun 07 2016
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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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STATUS
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approved
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