OFFSET
0,3
COMMENTS
For n >= 1, a(n) is the total number of compositions of positive integers less than or equal to n with distinct parts (cf. A032020).
For example, numbers of such compositions of 1,2,3,4,5 are 1,1,3,3,5. So a(5)=13.
FORMULA
a(n) - a(n-1) = A032020(n).
G.f.: (1/(1 - x)) * Sum_{i>=1} i!*x^(i*(i+1)/2) * Product_{j=1..i} 1/(1 - x^j). - Ilya Gutkovskiy, Apr 04 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Vladimir Shevelev, Dec 19 2013
EXTENSIONS
More terms from Peter J. C. Moses, Dec 19-20 2013
STATUS
approved