OFFSET
0,5
COMMENTS
Column 6 of A226048.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = (1/4)*( binomial(2*n,6) + 3*binomial(n,3) ).
a(n) = 7*a(n-1) -21*a(n-2) +35*a(n-3) -35*a(n-4) +21*a(n-5) -7*a(n-6) +a(n-7) with n>6, a(0)=a(1)=a(2)=0, a(3)=1, a(4)=10, a(5)=60, a(6)=246.
G.f.: x^3*(1+3*x+11*x^2+x^3)/(1-x)^7. [Bruno Berselli, Aug 27 2013]
MATHEMATICA
CoefficientList[Series[x^3 (1 + 3 x + 11 x^2 + x^3) / (1 - x)^7, {x, 0, 50}], x] (* Vincenzo Librandi, Sep 04 2013 *)
PROG
(R) a <- 0
for(n in 1:40) a[n+1] <- (1/4)*(choose(2*n, 6) + 3*choose(n, 3)) a
(Magma) [(1/4)*(Binomial(2*n, 6) + 3*Binomial(n, 3)): n in [0..50]]; // Vincenzo Librandi, Sep 04 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Yosu Yurramendi, María Merino, Aug 26 2013
EXTENSIONS
More terms from Vincenzo Librandi, Sep 04 2013
STATUS
approved