A061524 Surround numbers of an n X 2 rectangle when n is even.

224, 705, 1600, 3065, 5280, 8449, 12800, 18585, 26080, 35585, 47424, 61945, 79520, 100545, 125440, 154649, 188640, 227905, 272960, 324345, 382624, 448385, 522240, 604825, 696800, 798849, 911680, 1036025, 1172640, 1322305, 1485824, 1664025

Offset

2,1

Comments

See A061525 for odd n.

Links

Table of n, a(n) for n=2..33.

E. J. Friedman, Math. Magic: May, 1999

Formula

a(n) = (n^4 + 32n^3 + 344n^2 + 768n + 400)/16 for even n.

From Chai Wah Wu, Dec 20 2019: (Start)

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n > 6.

G.f.: x^2*(-25*x^4 + 125*x^3 - 315*x^2 + 415*x - 224)/(x - 1)^5. (End)

Crossrefs

Cf. A047875 A061525.

Sequence in context: A331371 A094209 A158227 * A156813 A233875 A233869

Adjacent sequences: A061521 A061522 A061523 * A061525 A061526 A061527

Keyword

easy,nonn

Author

Jason Earls, May 03 2001

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001

Status

approved