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A061524 Surround numbers of an n X 2 rectangle when n is even. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,1
COMMENTS
See A061525 for odd n.
LINKS
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
Sequence in context: A331371 A094209 A158227 * A156813 A233875 A233869
KEYWORD
easy,nonn
AUTHOR
Jason Earls, May 03 2001
EXTENSIONS
More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001
STATUS
approved

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Last modified April 12 06:13 EDT 2024. Contains 371623 sequences. (Running on oeis4.)