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A244214
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a(n) = binomial(2*c-1, c-1) (mod c^3), where c is the n-th composite.
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4
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35, 30, 291, 253, 378, 782, 2404, 1260, 291, 3378, 410, 7899, 3996, 6030, 126, 10988, 11188, 5180, 19712, 8483, 5334, 34394, 1841, 21410, 20580, 39556, 38810, 64260, 35972, 66060, 36504, 61326, 1716, 123628, 49140, 63748, 124392, 20091, 99388, 157767, 24392
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OFFSET
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1,1
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COMMENTS
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A counterexample to the converse of Wolstenholme's theorem (CWT) must have a(n) = 1. No such counterexample is known and if CWT holds, then a(n) > 1 for all n. If the square of a prime p is a counterexample to CWT, that prime satisfies the Wolstenholme congruence modulo p^6 (Cf. McIntosh (1995), p. 387).
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LINKS
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MATHEMATICA
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Mod[Binomial[2#-1, #-1], #^3]&/@Select[Range[100], CompositeQ] (* Harvey P. Dale, May 03 2023 *)
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PROG
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(PARI) forcomposite(c=1, 100, print1(lift(Mod(binomial(2*c-1, c-1), c^3)), ", "))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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