OFFSET
1,1
COMMENTS
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
a(1)=3, a(2)=23, a(3)=72, a(4)=162; for n>4, a(n)=4*a(n-1)-6*a(n-2)+4*a(n-3)-a(n-4).
G.f.: x*(3 + 11*x - 2*x^2)/(1 - x)^4.
MATHEMATICA
CoefficientList[Series[(3 + 11 x - 2 x^2)/(1 - x)^4, {x, 0, 50}], x] (* Vincenzo Librandi, Oct 12 2013 *)
PROG
(PARI) a(n) = n*(4*n^2 + 5*n - 3)/2; \\ Michel Marcus, Oct 11 2013
(Magma) [n*(4*n^2+5*n-3)/2: n in [1..40]]; // Vincenzo Librandi, Oct 12 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Zak Seidov, Mar 11 2007
STATUS
approved