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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. 16
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; refs; listen; history; internal format)
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: A178415 A076274 A058989 * A206297 A136252 A187212

Adjacent sequences:  A049688 A049689 A049690 * A049692 A049693 A049694

KEYWORD

nonn

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

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Last modified February 17 19:13 EST 2012. Contains 206085 sequences.