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