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A125273 Eigensequence of triangle A085478: a(n) = Sum_{k=0..n-1} A085478(n-1,k)*a(k) for n > 0 with a(0)=1. 10
1, 1, 2, 6, 23, 106, 567, 3434, 23137, 171174, 1376525, 11934581, 110817423, 1095896195, 11487974708, 127137087319, 1480232557526, 18075052037054, 230855220112093, 3076513227516437, 42686898298650967, 615457369662333260 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..21.

Guo-Niu Han, Enumeration of Standard Puzzles

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

Jeffrey B. Remmel, Consecutive Up-down Patterns in Up-down Permutations, Electron. J. Combin., 21 (2014), #P3.2.

FORMULA

a(n) = Sum_{k=0..n-1} binomial(n+k-1, n-k-1)*a(k) for n > 0 with a(0)=1.

G.f. satisfies: A(x) = 1 + x*A( x/(1-x)^2 ) / (1-x). - Paul D. Hanna, Aug 15 2007

EXAMPLE

a(3) = 1*(1) + 3*(1) + 1*(2) = 6;

a(4) = 1*(1) + 6*(1) + 5*(2) + 1*(6) = 23;

a(5) = 1*(1) + 10*(1) + 15*(2) + 7*(6) + 1*(23) = 106.

Triangle A085478(n,k) = binomial(n+k, n-k) begins:

  1;

  1,  1;

  1,  3,  1;

  1,  6,  5,  1;

  1, 10, 15,  7,  1;

  1, 15, 35, 28,  9,  1; ...

where g.f. of column k = 1/(1-x)^(2*k+1).

MATHEMATICA

A125273=ConstantArray[0, 20]; A125273[[1]]=1; Do[A125273[[n]]=1+Sum[A125273[[k]]*Binomial[n+k-1, n-k-1], {k, 1, n-1}]; , {n, 2, 20}]; Flatten[{1, A125273}] (* Vaclav Kotesovec, Dec 10 2013 *)

PROG

(PARI) a(n)=if(n==0, 1, sum(k=0, n-1, a(k)*binomial(n+k-1, n-k-1)))

CROSSREFS

Cf. A085478; A125274 (variant).

Sequence in context: A288912 A193321 A263780 * A187761 A277176 A130908

Adjacent sequences:  A125270 A125271 A125272 * A125274 A125275 A125276

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Nov 26 2006

STATUS

approved

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Last modified February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)