

A086640


Arrange n^2 octagons that each have area 7 so that they leave (n1)^2 square gaps each with area 2; a(n) is the total area of these polygons.


0



7, 30, 71, 130, 207, 302, 415, 546, 695, 862, 1047, 1250, 1471, 1710, 1967, 2242, 2535, 2846, 3175, 3522, 3887, 4270, 4671, 5090, 5527, 5982, 6455, 6946, 7455, 7982, 8527, 9090, 9671, 10270, 10887, 11522, 12175, 12846, 13535, 14242, 14967, 15710
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OFFSET

1,1


REFERENCES

Keith Devlin, "The language of mathematics", Henry Holt, NY, plate 9 after p. 249.


LINKS

Table of n, a(n) for n=1..42.
Index entries for linear recurrences with constant coefficients, signature (3,3,1).


FORMULA

a(n) = 9n^24n+2.
G.f. x*(2*x+7)*(1+x) / (x1)^3 .  R. J. Mathar, Sep 15 2012


PROG

(PARI) a(n)=9*n^24*n+2 \\ Charles R Greathouse IV, Jun 17 2017


CROSSREFS

Sequence in context: A063148 A116283 A139274 * A083474 A030440 A256225
Adjacent sequences: A086637 A086638 A086639 * A086641 A086642 A086643


KEYWORD

nonn,easy,less


AUTHOR

Jun Mizuki (suzuki32(AT)sanken.osakau.ac.jp), Jul 26 2003


EXTENSIONS

Edited and extended by David Wasserman, Jun 20 2007


STATUS

approved



