OFFSET
0,3
COMMENTS
a(n) = n * A001045(n+1).
This sequence is the sum of several triangles of integers (see formula section)
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,3,-4,-4).
FORMULA
G.f.: x*(1 + 4*x)/( 2*x^2+x-1)^2
a(n) = n*(2^(n + 1) + (-1)^n)/3
a(n)= sum( sum( (-1)^(j+k)*(j+k)*C(n-k+j,j), j=0..k), k=0..n)
a(n)= sum( n*C(n, k)*2F1( (1, -k); -n )(-1), k=0..n)
a(n)=sum( sum( (-1)^j*n*C(n-j,k-j), j=0..k), k=0..n)
a(n)= sum( (1+2*k)*C(n+1, k+1)*2F1( (1, n+2); k+2 )(-1) - C(n+2, k+2) 2F1( (2, n+3); k+3 )(-1) - (-1)^(k) * 2^(k-n-2) * (n-3*k+1) , k=0..n)
with C(n,k) the binomial coefficient and 2F1( ) the hypergeometric function.
MATHEMATICA
Table[Sum[n Binomial[n, k] HypergeometricPFQ[{1, -k}, {-n}, -1], {k, 0, n}], {n, 0, 35}]
CoefficientList[Series[(x*(1 + 4*x))/(2*x^2 + x - 1)^2, {x, 0, 100}], x] (* Vincenzo Librandi, Oct 21 2012 *)
PROG
(Magma) [n*(2^(n + 1) + (-1)^n)/3: n in [0..35]]; // Vincenzo Librandi, Oct 21 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Olivier Gérard, Jul 26 2011
STATUS
approved