

A098181


Odd numbers with two times the positive even numbers repeated in order between them.


4



1, 3, 4, 4, 5, 7, 8, 8, 9, 11, 12, 12, 13, 15, 16, 16, 17, 19, 20, 20, 21, 23, 24, 24, 25, 27, 28, 28, 29, 31, 32, 32, 33, 35, 36, 36, 37, 39, 40, 40, 41, 43, 44, 44, 45, 47, 48, 48, 49, 51, 52, 52, 53, 55, 56, 56, 57, 59, 60, 60, 61, 63, 64, 64, 65, 67, 68, 68, 69, 71, 72, 72
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OFFSET

0,2


COMMENTS

Essentially partial sums of A007877.


LINKS

Table of n, a(n) for n=0..71.


FORMULA

G.f. : (1+x)/((1x)^2(1+x^2)); a(n)=(2n+3)/2cos(pi*n/2)/2+sin(pi*n/2)/2; a(n)=2a(n1)2a(n2)+2a(n3)a(n4).
a(n)=floor(C(n+3, 2)/2)floor(C(n+1, 2)/2)  Paul Barry, Jan 01 2005
a(4n)=4n+1, a(4n+1)=4n+3, a(4n+2)=4n+4, a(4n+3)=4n+4 .  Philippe Deléham, Apr 06 2007


CROSSREFS

Cf. A098180.
Sequence in context: A113454 A157726 A082223 * A111914 A051665 A028263
Adjacent sequences: A098178 A098179 A098180 * A098182 A098183 A098184


KEYWORD

easy,nonn


AUTHOR

Paul Barry, Aug 30 2004


STATUS

approved



