OFFSET
0,1
COMMENTS
For n >= 3, also the disorder number of the pan graph.
LINKS
Eric Weisstein's World of Mathematics, Disorder Number.
Eric Weisstein's World of Mathematics, Pan Graph.
Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1).
FORMULA
a(n) = 2*a(n-1)-2*a(n-3)+1*a(n-4).
G.f.: x*(-2+3*x^2-3*x^3)/((-1+x)^3*(1+x)).
After initial terms same as {A114113}+2, {A236453}+1, ({A081353}+1)/2 + 2. Hugo Pfoertner, Oct 10 2024.
MATHEMATICA
Table[(n (n - 1) + 5 + (-1)^n)/2, {n, 20}]
LinearRecurrence[{2, 0, -2, 1}, {2, 4, 5, 9}, {0, 20}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Oct 08 2024
STATUS
approved