OFFSET
1,1
FORMULA
Conjectures from Colin Barker, Oct 25 2019: (Start)
G.f.: x*(4 + 5*x + 5*x^2 + 5*x^3 + 4*x^4 + 2*x^5) / (1 - x)^2.
a(n) = 2*a(n-1) - a(n-2) for n>6.
a(n) = 25*n-56 for n>4.
(End)
EXAMPLE
If you have 1 coin you can have 4 different totals: 1, 5, 10 and 25. If you have 2 coins, you can have 10 totals: 2, 6, 10, 11, 15, 20, 26, 30, 35, 50. Notice that the same total appears twice: 10 is one dime and two nickels. Hence a(2) = 13.
MATHEMATICA
Join[{4, 13, 27, 46}, Range[69, 2000, 25]] (* Vladimir Joseph Stephan Orlovsky, Jun 15 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Tanya Khovanova, Jul 28 2006
STATUS
approved