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A028236 If n = Product (p_j^k_j), a(n) = numerator of Sum 1/p_j^k_j. 4
1, 1, 1, 1, 1, 5, 1, 1, 1, 7, 1, 7, 1, 9, 8, 1, 1, 11, 1, 9, 10, 13, 1, 11, 1, 15, 1, 11, 1, 31, 1, 1, 14, 19, 12, 13, 1, 21, 16, 13, 1, 41, 1, 15, 14, 25, 1, 19, 1, 27, 20, 17, 1, 29, 16, 15, 22, 31, 1, 47, 1, 33, 16, 1, 18, 61, 1, 21, 26, 59, 1, 17, 1, 39, 28, 23, 18, 71, 1, 21, 1, 43 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

K. Brockhaus, Table of n, a(n) for n = 1..10000 [From Klaus Brockhaus, Nov 06 2010]

FORMULA

Fraction is additive with a(p^e) = 1/p^e.

a(n) = sum(n/a141809(n,k): k=1..A001221(n)). - Reinhard Zumkeller, Nov 10 2013

PROG

(MAGMA) a028236:=func< k | k eq 1 select 1 else Numerator(&+[ f[i, 1]^-f[i, 2]: i in [1..#f] ]) where f is Factorization(k) >; [ a028236(n):n in [1..82] ]; [From Klaus Brockhaus, Nov 06 2010]

(Haskell)

a028236 n = sum $ map (div n) $ a141809_row n

-- Reinhard Zumkeller, Nov 10 2013

CROSSREFS

Denominator is n (A000027).

Sequence in context: A284254 A250097 A028235 * A066504 A292771 A168677

Adjacent sequences:  A028233 A028234 A028235 * A028237 A028238 A028239

KEYWORD

nonn,easy,frac

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Erich Friedman.

STATUS

approved

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Last modified February 23 23:56 EST 2018. Contains 299595 sequences. (Running on oeis4.)