OFFSET
1,2
COMMENTS
Every natural number up to sum(a[1], a[i]) can be written as adding or subtracting unique entries up to a(i).
LINKS
The Ben Paul Thurston Blog, Balance scale series
FORMULA
a(i+1)= 1+2*sum(a[1], a[i]) (proved).
EXAMPLE
17 = 21-7+1+2, 18=21-1-2, 19=17+2.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Ben Paul Thurston, Dec 09 2015
STATUS
approved