OFFSET
1,3
COMMENTS
Column sums of shifted Pascal-like array:
1..1..10..10..100..100.1000.1000
......-1..-2..-30..-40.-500.-600
................1....3...60..100
.........................-1...-4
-------------------------------- +
1..1...9...8...71...63..559..496
Decimal expansion of ratio n/(n+1) is accumulation of Catalan numbers; (5 +/- sqrt(15)).
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,8,0,-1).
FORMULA
For n odd a(n) = 10*a(n-1) - a(n-2), for n even a(n) = a(n-1) - a(n-2); with a(0) = 0, a(1) = 1.
G.f.: x*(1+x+x^2) / ( 1-8*x^2+x^4 ). - R. J. Mathar, Nov 11 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mark Dols, May 04 2010
STATUS
approved