OFFSET
1,14
COMMENTS
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
Tanya Khovanova, There are no coincidences, arXiv preprint 1410.2193 [math.CO], 2014.
FORMULA
a(n)=0 if n is odd; otherwise, a(n) = ( 3^(r-1) - 1)/2, where r is the number of 1's in the binary expansion of n.
EXAMPLE
For example, a(14)=4; the four 3-tuples are (1,6,7), (2,5,7), (3,4,7) and (3,5,6).
PROG
(PARI) A128975(n) = if(n%2, 0, (1/2)*((3^(hammingweight(n)-1))-1)); \\ Antti Karttunen, Sep 25 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jacob A. Siehler, Apr 29 2007
STATUS
approved