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A281662
(Denominator of Bernoulli(2*n)) read mod n.
2
0, 0, 0, 2, 1, 0, 6, 6, 6, 0, 6, 6, 6, 2, 12, 14, 6, 12, 6, 10, 0, 8, 6, 18, 16, 4, 15, 2, 6, 0, 6, 30, 9, 30, 31, 30, 6, 30, 3, 10, 6, 0, 6, 30, 3, 30, 6, 42, 6, 30, 42, 30, 6, 30, 33, 6, 42, 30, 6, 30, 6, 30, 42, 62, 1, 24, 6, 30, 42, 50, 6, 6, 6, 30, 72, 30, 61
OFFSET
1,4
COMMENTS
Odd terms at: 5, 27, 33, 35, 39, 45, 55, 65, 77, 81, 99, 105, 121, etc. - Robert G. Wilson v, Jan 26 2017
LINKS
FORMULA
a(n) = A002445(n) mod n.
MATHEMATICA
f[n_] := Mod[Denominator[BernoulliB[2 n]], n]; Array[f, 77] (* Robert G. Wilson v, Jan 26 2017 *)
PROG
(Ruby)
def bernoulli(n)
ary = []
a = []
(0..n).each{|i|
a << 1r / (i + 1)
i.downto(1){|j| a[j - 1] = j * (a[j - 1] - a[j])}
ary << a[0]
}
ary
end
def A281662(n)
a = bernoulli(2 * n)
(1..n).map{|i| a[2 * i].denominator % i}
end
(PARI) a(n) = denominator(bernfrac(2*n)) % n; \\ Michel Marcus, Jan 29 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jan 26 2017
STATUS
approved