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Revision History for A126725

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A126725

a(1)=0, a(2)=1; for n>2, a(n) = C(n,2)*(1+a(n-2)).
(history; published version)

#30 by Charles R Greathouse IV at Thu Sep 08 08:45:29 EDT 2022

PROG

(MAGMAMagma) I:=[0, 1]; [n le 2 select I[n] else Binomial(n, 2)*(1+Self(n-2)): n in [1..35]]; // Vincenzo Librandi, Mar 17 2015

Discussion

Thu Sep 08

08:45

OEIS Server: https://oeis.org/edit/global/2944

#29 by N. J. A. Sloane at Fri Mar 27 21:30:20 EDT 2015

STATUS

proposed

approved

#28 by Jon E. Schoenfield at Fri Mar 27 20:23:06 EDT 2015

STATUS

editing

proposed

#27 by Jon E. Schoenfield at Fri Mar 27 20:23:04 EDT 2015

NAME

a(1)=0, a(2)=1; for n>2, a(n) = binomialC(n,2)*(1+a(n-2)).

COMMENTS

a(n) is also the maximum number of ways to place node pairs in an area formed by n 1x1 1 X 1 squares. - Theodore M. Mishura, Mar 20 2015

FORMULA

a(n) = A087214(n) - 1. - N. J. A. Sloane, Feb 15 2007

STATUS

reviewed

editing

#26 by Michel Marcus at Fri Mar 27 03:44:49 EDT 2015

STATUS

proposed

reviewed

#25 by Vaclav Kotesovec at Fri Mar 20 13:48:20 EDT 2015

STATUS

editing

proposed

Discussion

Sun Mar 22

14:21

Michel Marcus: The area formed by n 1x1 squares , is it a rectangle ?

Mon Mar 23

00:25

Theodore M. Mishura: The shape the area formed by n 1x1 squares takes on is irrelevant; what is important is that there are exactly n units of 1 area, and that each node in a given node pair takes up exactly 1 unit of 1 area.

#24 by Vaclav Kotesovec at Fri Mar 20 13:35:19 EDT 2015

CROSSREFS

Cf. A087214.

STATUS

proposed

editing

#23 by Vaclav Kotesovec at Fri Mar 20 13:30:49 EDT 2015

STATUS

editing

proposed

#22 by Vaclav Kotesovec at Fri Mar 20 13:21:36 EDT 2015

FORMULA

a(n) ~ n! * (exp(sqrt(2)) + (-1)^n * exp(-sqrt(2))) / 2^(n/2+1). - Vaclav Kotesovec, Mar 20 2015

STATUS

proposed

editing

#21 by Theodore M. Mishura at Fri Mar 20 09:15:31 EDT 2015

STATUS

editing

proposed