OFFSET
0,3
REFERENCES
Alan Sutcliffe, Divisors and Common Factors in Sets of Integers, awaiting publication.
FORMULA
n*(n-1)*2^(n-4+2^(n-1))
EXAMPLE
a(3)=48 since the 16 subsets of the sets ( ) (1) (2) (1,2) are ( ) (( )) ((1)) ((2)) ((1,2)) (( ) (1)) (( ) (2)) (( ) (1,2)) ((1) (2)) ((1) (1,2)) ((2) (1,2)) (( ) (1) (2)) (( ) (1) (1,2)) (( ) (2) (1,2)) ((1) (2) (1,2)) (( ) (1) (2) (1,2)) and the sum of the 32 integer elements is 48.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Alan Sutcliffe (alansut(AT)ntlworld.com), Aug 13 2003
STATUS
approved