OFFSET
1,1
LINKS
Nicolo Sartori di Borgoricco, Proof that formula is correct
Index entries for linear recurrences with constant coefficients, signature (110,-1000).
FORMULA
a(n) = 3*10^(2*n-1) + 5*10^(n-1).
G.f.: 5*x*(7 - 160*x)/(1 - 110*x + 1000*x^2). - Stefano Spezia, Apr 21 2021
a(n) = 110*a(n-1)-1000*a(n-2). - Wesley Ivan Hurt, Apr 26 2021
EXAMPLE
a(1) = 2 + 5 + 4 + 6 + 8 + 10 = 3*10^(2*1-1) + 5*10^(1-1) = 35.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Nicolo Sartori di Borgoricco, Apr 20 2021
STATUS
approved