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%I #9 Aug 13 2020 14:01:06
%S 224,705,1600,3065,5280,8449,12800,18585,26080,35585,47424,61945,
%T 79520,100545,125440,154649,188640,227905,272960,324345,382624,448385,
%U 522240,604825,696800,798849,911680,1036025,1172640,1322305,1485824,1664025
%N Surround numbers of an n X 2 rectangle when n is even.
%C See A061525 for odd n.
%H E. J. Friedman, <a href="https://erich-friedman.github.io/mathmagic/0599.html">Math. Magic: May, 1999</a>
%F a(n) = (n^4 + 32n^3 + 344n^2 + 768n + 400)/16 for even n.
%F From _Chai Wah Wu_, Dec 20 2019: (Start)
%F a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n > 6.
%F G.f.: x^2*(-25*x^4 + 125*x^3 - 315*x^2 + 415*x - 224)/(x - 1)^5. (End)
%Y Cf. A047875 A061525.
%K easy,nonn
%O 2,1
%A _Jason Earls_, May 03 2001
%E More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001
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