OFFSET
1,3
COMMENTS
This sequence can also be defined as follows: a(n) is the unique sequence such that a(1) = a(2) = 1 and the second differences of a(n) are 2, except that the a(n)th second difference is 1 for all n. In other words, if b(n) = a(n+2) - 2a(n+1) + a(n) is the second-difference function for a(n), x(n) = 2 - b(n) is the characteristic function for a(n). - Joel B. Lewis, Mar 16 2007
EXAMPLE
a(6) = min(5,1) + min(5,1) + min(5,2) + min(5,4) + min(5,8) = 1 + 1 + 2 + 4 + 5 = 13.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Leroy Quet, Aug 04 2000
STATUS
approved