OFFSET
1,2
COMMENTS
The 2-digit numbers distributed according to the sum of their digits n.
Symmetrical sequence; a(n) = a(19 - n).
FORMULA
G.f.: (1 - x^10)*(x - x^10)/(1 - x)^2.
a(n) = (19-abs(n-9)-abs(n-10))/2 for n=1..18. - Wesley Ivan Hurt, Jul 09 2017
EXAMPLE
n(5) = 5 because there are 5 numbers whose digits sum = 5 (14, 23, 32, 41, 50).
CROSSREFS
KEYWORD
fini,full,nonn,base
AUTHOR
Miquel Cerda, Jul 09 2017
STATUS
approved