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A117991 Number of distinct rational numbers that can be written as fractions of the first n composite numbers. 1
1, 3, 7, 11, 19, 23, 35, 41, 53, 59, 67, 77, 101, 109, 131, 161, 179, 197, 205, 227, 247, 289, 317, 333, 381, 407, 431, 445, 473, 495, 555, 575, 629, 657, 693, 729, 751, 801, 835, 877, 957, 975, 1059, 1097, 1147, 1209, 1235, 1283, 1335, 1367, 1397, 1499, 1539 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = 2*A117992(n) + 1.

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

n=3, the first 3 composite numbers are 4,6 and 8:

a(3) = #{4/4, 4/6, 4/8, 6/4, 6/6, 6/8, 8/4, 8/6, 8/8} =

= #{1/2, 2/3, 3/4, 1/1, 4/3, 3/2, 2/1} = 7.

CROSSREFS

Cf. A018805.

Sequence in context: A181516 A002145 A092109 * A118260 A018805 A191037

Adjacent sequences:  A117988 A117989 A117990 * A117992 A117993 A117994

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Apr 08 2006

STATUS

approved

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Last modified September 1 19:34 EDT 2014. Contains 246317 sequences.