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A099001 (Sum 1/k) (Product k), where both the sum and product are over those k where 1 <= k <= n/2 and GCD(k,n) = 1. 1
1, 1, 1, 3, 1, 11, 4, 14, 4, 274, 6, 1764, 23, 106, 176, 109584, 47, 1026576, 300, 6960, 1689, 120543840, 552, 26854848, 19524, 7962160, 34986, 283465647360, 1312, 4339163001600, 4098240, 164944640, 4098240, 13833580032, 133542, 22376988058521600, 71697105 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,4

LINKS

Alois P. Heinz, Table of n, a(n) for n = 2..900

EXAMPLE

a(8) = (1 +1/3)*1*3 = 4 because 1 and 3 are those positive integers <= 8/2 and coprime to 8.

MAPLE

b:=proc(n) local B, k: B:={}: for k from 1 to n/2 do if gcd(k, n)=1 then B:=B union {k} else B:=B fi od end: a:=proc(n) add(1/b(n)[j], j=1..nops(b(n)))*product(b(n)[j], j=1..nops(b(n))) end: seq(a(n), n=2..40); # Emeric Deutsch, Apr 22 2006

# second Maple program:

a:= n-> (l-> mul(i, i=l)*add(1/i, i=l))(

         select(x-> igcd(x, n)=1, [$1..n/2])):

seq(a(n), n=2..40);  # Alois P. Heinz, May 22 2015

CROSSREFS

Cf. A056855.

Sequence in context: A256589 A229834 A120291 * A119947 A165674 A027446

Adjacent sequences:  A098998 A098999 A099000 * A099002 A099003 A099004

KEYWORD

nonn

AUTHOR

Leroy Quet, Nov 13 2004

EXTENSIONS

More terms from Emeric Deutsch, Apr 22 2006

STATUS

approved

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Last modified October 15 00:14 EDT 2019. Contains 328025 sequences. (Running on oeis4.)