

A227043


Numerator of harmonic mean H(n,2), n>= 0.


1



0, 4, 2, 12, 8, 20, 3, 28, 16, 36, 10, 44, 24, 52, 7, 60, 32, 68, 18, 76, 40, 84, 11, 92, 48, 100, 26, 108, 56, 116, 15, 124, 64, 132, 34, 140, 72, 148, 19, 156, 80, 164, 42, 172, 88, 180, 23, 188, 96, 196, 50, 204, 104, 212, 27, 220, 112, 228, 58, 236, 120
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OFFSET

0,2


COMMENTS

a(n) = numerator(H(n,2)) = numerator(4*n/(n+2)), n>=0, with H(n,2) the harmonic mean of n and 2.
The corresponding denominator is given in A000265(n+2), n>= 0.
a(n+2), n>=0, is the second column (m=2) of the triangle A227041.


LINKS

Table of n, a(n) for n=0..60.


FORMULA

a(n) = numerator(4*n/(n+2)), n >= 0.
a(n) = 4*n/gcd(n+2,4*n) = 4*n/gcd(n+2,8), n >= 0.


EXAMPLE

The rationals H(n,2) begin:
0, 4/3, 2, 12/5, 8/3, 20/7, 3, 28/9, 16/5, 36/11, 10/3, 44/13, 24/7, 52/15, 7/2, 60/17, ...


CROSSREFS

Cf. A227041(n+2,2), A000265(n+2) (denominator), n >= 0.
Sequence in context: A191441 A152664 A167591 * A143376 A111667 A323825
Adjacent sequences: A227040 A227041 A227042 * A227044 A227045 A227046


KEYWORD

nonn,easy,frac


AUTHOR

Wolfdieter Lang, Jul 01 2013


STATUS

approved



