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 A185399 As p runs through the primes, sequence gives denominator of Sum_{k=1..p-1} 1/k. 5
 1, 2, 12, 20, 2520, 27720, 720720, 4084080, 5173168, 80313433200, 2329089562800, 13127595717600, 485721041551200, 2844937529085600, 1345655451257488800, 3099044504245996706400, 54749786241679275146400, 3230237388259077233637600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS T. D. Noe, Table of n, a(n) for n = 1..100 R. Mestrovic, Wolstenholme's theorem: Its Generalizations and Extensions in the last hundred and fifty years (1862-2011), arXiv:1111.3057 [math.NT], 2011. FORMULA a(n) = denominator(sum((k+1)/(p-k-1), k=0..p-2)), where p = the n-th prime. - Gary Detlefs, Jan 12 2012 a(n) = numerator(H(p)/H(p-1)) - denominator(H(p)/H(p-1)), where p is the n-th prime and H(n) is the n-th harmonic number. - Gary Detlefs, Apr 21 2013 MAPLE f2:=proc(n) local p; p:=ithprime(n); denom(add(1/i, i=1..p-1)); end proc; [seq(f2(n), n=1..20)]; MATHEMATICA nn = 20; sm = 0; t = Table[sm = sm + 1/k; Denominator[sm], {k, Prime[nn]}]; Table[t[[p - 1]], {p, Prime[Range[nn]]}] (* T. D. Noe, Apr 23 2013 *) PROG (PARI) a(n) = denominator(sum(k=1, prime(n)-1, 1/k)); \\ Michel Marcus, Dec 05 2018 (MAGMA) [Denominator(HarmonicNumber(NthPrime(n)-1)): n in [1..40]]; // Vincenzo Librandi, Dec 05 2018 CROSSREFS Cf. A001008, A002805 (numerators and denominators of harmonic numbers). Cf. A061002, A193758. Sequence in context: A331947 A145634 A145610 * A096108 A098941 A231875 Adjacent sequences:  A185396 A185397 A185398 * A185400 A185401 A185402 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 21 2012 STATUS approved

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Last modified May 13 05:02 EDT 2021. Contains 343836 sequences. (Running on oeis4.)