OFFSET
1,1
FORMULA
a(n) = (1+a(1)+a(2)+...+a(n-1)-n/2)*(n-1).
EXAMPLE
The sets begin {1,2},{3,4},{5,6,...,9,10,11},{12,13,...,38,39,40,41},...
PROG
(PARI) a(n) = if (n==1, 2, (1+sum(k=1, (n-1), a(k)) - n/2)*(n-1)); \\ Michel Marcus, Sep 10 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Floor van Lamoen, Jan 17 2002
EXTENSIONS
More terms from Michel Marcus, Sep 10 2017
STATUS
approved