A055980 - OEIS

A055980

a(n) = floor(Sum_{i=1..n} 1/i).

1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,4

COMMENTS

If we choose at random (uniformly) a permutation in the symmetric group S_n then a(n) is the expected number of cycles (rounded down) in the cycle decomposition of the permutation. - Dan Fux (dan.fux(AT)OpenGaia.com or danfux(AT)OpenGaia.com), Oct 17 2001

a(n) = A214075(n,n-1) for n > 0. - Reinhard Zumkeller, Jul 03 2012

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

L. D. Kudryavtsev, Harmonic series, The Encyclopedia of Mathematics.

Eric Weisstein's World of Mathematics, High-Water Mark

FORMULA

a(n) ~ log(n) - Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 25 2001

a(n) = floor[A001008(n)/A002805(n)]. - Lekraj Beedassy, Sep 17 2006

MATHEMATICA

Floor[HarmonicNumber[Range[110]]] (* Harvey P. Dale, May 22 2021 *)

PROG

(Haskell)

import Data.Ratio ((%), denominator)

a055980 = floor . sum . map (1 %) . enumFromTo 1

a055980_list = map floor $ scanl1 (+) $ map (1 %) [1..]

-- Reinhard Zumkeller, Jul 03 2012

CROSSREFS

Cf. A002387, A004080 (indices of records).

Sequence in context: A191517 A303370 A082528 * A076080 A134914 A372406

Adjacent sequences: A055977 A055978 A055979 * A055981 A055982 A055983

KEYWORD

nonn

AUTHOR

Henry Bottomley, Jul 20 2000

STATUS

approved

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