A046886 - OEIS

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A046886

Number of divisors d of 2n satisfying (d+1) = prime or number of prime factors of the denominator of the even Bernoulli numbers.

2, 3, 3, 3, 3, 5, 2, 4, 4, 4, 3, 5, 2, 4, 5, 4, 2, 7, 2, 5, 4, 4, 3, 6, 3, 4, 4, 4, 3, 8, 2, 4, 5, 3, 4, 8, 2, 3, 4, 6, 3, 7, 2, 5, 6, 4, 2, 7, 2, 5, 4, 4, 3, 8, 4, 6, 3, 4, 2, 9, 2, 3, 6, 4, 4, 7, 2, 4, 5, 6, 2, 9, 2, 4, 6, 3, 3, 8, 2, 6, 5, 4, 3, 7, 3, 4, 4, 6, 3, 11, 2, 4, 3, 3, 4, 8, 2, 5, 7, 6, 2, 6, 2, 5

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OFFSET

1,1

COMMENTS

From von Staudt-Clausen theorem.

REFERENCES

G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 5th ed., Oxford Univ. Press, 1979, Th. 118.

Hans Rademacher, Topics in Analytic Number Theory, Springer, 1973, Chap. 1.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A067513(2n). - R. J. Mathar, Aug 07 2022