A085781 a(n) = 2*binomial(2*n+1,n+1) - 2^n.

1, 4, 16, 62, 236, 892, 3368, 12742, 48364, 184244, 704408, 2702108, 10396504, 40108408, 155101136, 601047622, 2333540684, 9075004228, 35345001656, 137846004532, 538256825864, 2104096866568, 8233426533296, 32247595294492

Offset

0,2

Comments

Create a triangle with the first column being the n-th row of Pascal's triangle from A007318, T(r,0) = binomial(n,r). The other terms T(r,c) are defined as T(r,c-1) + T(r-1,c-1). The sum of all terms for each triangle having n+1 rows is a(n). Example for n=3: the triangle has four rows 1; 3,4; 3,6,10; 1,4,10,20 ; sum of all 10 elements in the triangle is 62=a(3). - J. M. Bergot, Jan 17 2013

Links

Table of n, a(n) for n=0..23.

Formula

a(n) = sum(sum(binomial(i,j), i=n..n+j), j=0..n) = 2*A001700(n)-A000079(n).

Conjecture: (n+1)*a(n) -2*(4*n+1)*a(n-1) +4*(5*n-3)*a(n-2) +8*(-2*n+3)*a(n-3)=0. - R. J. Mathar, Jan 25 2013

Maple

seq(2*binomial(2*n+1, n+1)-2^n, n=0..25);

Mathematica

Table[2Binomial[2n+1, n+1]-2^n, {n, 0, 30}] (* Harvey P. Dale, Aug 30 2021 *)

Crossrefs

Sequence in context: A084859 A081666 A250346 * A113438 A268429 A195339

Adjacent sequences: A085778 A085779 A085780 * A085782 A085783 A085784

Keyword

nonn,easy

Author

Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jul 23 2003

Status

approved