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A225050 Number of shortest paths from one vertex of a cube (side = n units) to farthest vertex, along the grid on 3 surfaces meeting at another vertex. 1
1, 4, 24, 148, 920, 5754, 36204, 229128, 1458072, 9325030, 59905274, 386368008, 2500651244, 16234450288, 105680341560, 689579733648, 4509096746904, 29539804567230, 193843622021910, 1273932593379600, 8383551165082170, 55238332546851630, 364364231864557080 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..22.

FORMULA

a(n) = 2*binomial(3n,n) - binomial(2n,n).

MAPLE

A225050:=n->2*binomial(3*n, n)-binomial(2*n, n); seq(A225050(n), n=0..30); # Wesley Ivan Hurt, May 10 2014

MATHEMATICA

Table[2*Binomial[3 n, n] - Binomial[2 n, n], {n, 30}]

PROG

(PARI) a(n)=2*binomial(3*n, n)-binomial(2*n, n) \\ Charles R Greathouse IV, Apr 26 2013

CROSSREFS

Cf. A060774.

Sequence in context: A077613 A072949 A104531 * A045738 A215708 A192806

Adjacent sequences:  A225047 A225048 A225049 * A225051 A225052 A225053

KEYWORD

nonn,easy

AUTHOR

Ravichandran Subramanian, Apr 25 2013

STATUS

approved

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Last modified August 10 01:45 EDT 2020. Contains 336363 sequences. (Running on oeis4.)