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A166062 a(n) = denominator(Bernoulli(prime(n) - 1)). 4
2, 6, 30, 42, 66, 2730, 510, 798, 138, 870, 14322, 1919190, 13530, 1806, 282, 1590, 354, 56786730, 64722, 4686, 140100870, 3318, 498, 61410, 4501770, 33330, 4326, 642, 209191710, 1671270, 4357878, 8646, 4110, 274386, 4470, 2162622, 1794590070, 130074 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Divisibility through terms of A008578 is a consequence of the Staudt-Clausen theorem.

(Vaguely similar divisibility properties are considered in A165248 and A165943.)

The first 250 entries are all different. Is this true in general?

Would sorting the entries yield the full A090801?

a(n) > 1 is the largest number k such that x*y^p == y*x^p (mod k) for all integers x and y, where p = prime(n). Example: x*y^19 == y*x^19 (mod 798). - Michel Lagneau, Apr 19 2012

LINKS

Peter Luschny, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, von Staudt-Clausen Theorem.

FORMULA

a(n) = A027642(A008578(n)-1).

MAPLE

seq(denom(bernoulli(ithprime(n)-1)), n=1..38); # Peter Luschny, Jul 14 2019

MATHEMATICA

Table[Denominator[BernoulliB[n-1]], {n, Prime[Range[38]]}] (* Harvey P. Dale, Apr 22 2012 *)

PROG

(PARI) a(n)=denominator(bernfrac(prime(n)-1)) \\ Charles R Greathouse IV, Apr 30 2012

CROSSREFS

Cf. A071772, A110936.

Sequence in context: A286652 A265501 A090801 * A100194 A229882 A325986

Adjacent sequences:  A166059 A166060 A166061 * A166063 A166064 A166065

KEYWORD

nonn

AUTHOR

Paul Curtz, Oct 05 2009

EXTENSIONS

Edited by Peter Luschny, Jul 14 2019

STATUS

approved

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Last modified October 14 09:25 EDT 2019. Contains 327995 sequences. (Running on oeis4.)