|
|
A062992
|
|
Row sums of unsigned triangle A062991.
|
|
12
|
|
|
1, 3, 13, 67, 381, 2307, 14589, 95235, 636925, 4341763, 30056445, 210731011, 1493303293, 10678370307, 76957679613, 558403682307, 4075996839933, 29909606989827, 220510631755773, 1632599134961667, 12133359132082173
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
COMMENTS
|
a(n) = N(2; n,x=-1), with the polynomials N(2; n,x) defined in A062991.
|
|
LINKS
|
|
|
FORMULA
|
a(n) = (-1)^(n+1) + 2*Sum_{j = 0..n} (-1)^j*C(n-j)*2^(n-j) with C(n) := A000108(n) (Catalan).
G.f.: A(x) = (2*c(2*x) - 1)/(1 + x) with c(x) the g.f. of A000108.
a(n) = 1/(n+1) * Sum{k = 0..n} binomial(2*n+2, n-k)*binomial(n+k, k). - Paul Barry, May 11 2005
Rewritten: a(n) = (1 - 2*c(n, -2))*(-1)^(n+1), n >= , with c(n, x) := Sum_{k = 0..n} C(k)*x^k and C(k) := A000108(k) (Catalan). - Wolfdieter Lang, Oct 31 2005
Recurrence: (n+1)*a(n) = (7*n-5)*a(n-1) + 4*(2*n-1)*a(n-2). - Vaclav Kotesovec, Oct 13 2012
a(n) = hypergeometric([-n, n+1], [-n-1], 2). - Peter Luschny, Nov 30 2014
|
|
MATHEMATICA
|
Table[2*Sum[(-1)^j*Binomial[2*n-2*j, n-j]/(n-j+1)*2^(n-j), {j, 0, n}]-(-1)^n, {n, 0, 20}] (* Vaclav Kotesovec, Oct 13 2012 *)
|
|
PROG
|
(PARI) a(n)=polcoeff((1-2*x-sqrt(1-8*x+x^2*O(x^n)))/(2*x+2*x^2), n)
(PARI) a(n)=if(n<0, 0, polcoeff(serreverse((x-x^2)/(1+x)^2+O(x^(n+2))), n+1)) \\ Ralf Stephan
(Haskell)
(Sage)
def a(n): return hypergeometric([-n, n+1], [-n-1], 2)
[a(n).hypergeometric_simplify() for n in range(21)] # Peter Luschny, Nov 30 2014
|
|
CROSSREFS
|
Cf. A112707 (c(n, -m) triangle). Here m=2 is used. Row sums of A234950.
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|