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A104858 Partial sums of the little Schroeder numbers (A001003). 2
1, 2, 5, 16, 61, 258, 1161, 5440, 26233, 129282, 648141, 3294864, 16943733, 87983106, 460676625, 2429478144, 12893056497, 68802069506, 368961496469, 1987323655056, 10746633315501, 58321460916482, 317537398625945 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The subsequence of primes begins: 2, 5, 61, no more through a(30). [Jonathan Vos Post, Feb 12 2010]

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Guo-Niu Han, Enumeration of Standard Puzzles

Guo-Niu Han, Enumeration of Standard Puzzles [Cached copy]

FORMULA

G.f.=[1+z-sqrt(1-6z+z^2)]/[4z(1-z)].

Recurrence: (n+1)*a(n) = (7*n-2)*a(n-1) - (7*n-5)*a(n-2) + (n-2)*a(n-3). - Vaclav Kotesovec, Oct 17 2012

a(n) ~ sqrt(24+17*sqrt(2))*(3+2*sqrt(2))^n/(8*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Oct 17 2012

Define a triangle T(n,1) = T(n,n) = 1 for n = 1, 2, 3... and all other elements by T(r,c) = T(r,c-1) + T(r-1,c-1) + T(r-1,c). Its second column is A005408, its third column is A059993, and the sum of all terms in its row n is a(n-1). - J. M. Bergot, Dec 01 2012

MAPLE

G:=(1+z-sqrt(1-6*z+z^2))/4/z/(1-z): Gser:=series(G, z=0, 29): 1, seq(coeff(Gser, z^n), n=1..27);

MATHEMATICA

CoefficientList[Series[(1+x-Sqrt[1-6*x+x^2])/4/x/(1-x), {x, 0, 20}], x] (* Vaclav Kotesovec, Oct 17 2012 *)

CROSSREFS

Cf. A001003.

Sequence in context: A012051 A012159 A009736 * A178123 A138265 A275711

Adjacent sequences:  A104855 A104856 A104857 * A104859 A104860 A104861

KEYWORD

nonn

AUTHOR

Emeric Deutsch, Apr 24 2005

STATUS

approved

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Last modified February 21 14:36 EST 2018. Contains 299414 sequences. (Running on oeis4.)