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Search: id:A049691
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A049691 a(n)=T(n,n), array T as in A049687. Also a(n)=T(2n,2n), array T given by A049639. +0
15
0, 3, 5, 9, 13, 21, 25, 37, 45, 57, 65, 85, 93, 117, 129, 145, 161, 193, 205, 241, 257, 281, 301, 345, 361, 401, 425, 461, 485, 541, 557, 617, 649, 689, 721, 769, 793, 865, 901, 949, 981 (list; graph; listen)
OFFSET

0,2

FORMULA

a(n) is related to the sequence b(n) = |{(x, y): gcd(x, y) = 1, 1<=x, y<=n}| (A018805) as follows: a(n) = b(n - 1) + 2 (for n > 1). - Shawn Westmoreland (westmore(AT)math.utexas.edu), Jun 11 2003

CROSSREFS

Cf. A018805.

Sequence in context: A007042 A076274 A058989 this_sequence A136252 A141325 A146905

Adjacent sequences: A049688 A049689 A049690 this_sequence A049692 A049693 A049694

KEYWORD

nonn

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

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Last modified December 3 14:12 EST 2008. Contains 151279 sequences.


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