A265500 - OEIS

%I #9 Jan 09 2016 14:58:19

%S 1,2,7,21,52,167,501,1503,4509,13527,40581

%N Balance scale sequence.

%C Every natural number up to sum(a[1], a[i]) can be written as adding or subtracting unique entries up to a(i).

%H The Ben Paul Thurston Blog, <a href="http://benpaulthurstonblog.blogspot.com/2015/12/combination-series.html">Balance scale series</a>

%F a(i+1)= 1+2*sum(a[1], a[i]) (proved).

%e 17 = 21-7+1+2, 18=21-1-2, 19=17+2.

%K nonn,more

%O 1,2

%A _Ben Paul Thurston_, Dec 09 2015