OFFSET
1,1
REFERENCES
M. Gardner, Knotted Doughnuts and Other Mathematical Entertainments. Freeman, NY, 1986, p. 76.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1,1,-3,3,-1).
FORMULA
G.f.: -2*x*(-4-3*x^2-2*x^3+x^4)/(1+x)/(x^2+1)/(x-1)^4.
a(n) = 17*n/6+3/4+2*n^3/3+3*n^2+A132429(n+3)/4. - R. J. Mathar, Sep 27 2009
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-4) - 3*a(n-5) + 3*a(n-6) - a(n-7). - Vincenzo Librandi, Dec 19 2012
MATHEMATICA
CoefficientList[Series[-2*(- 4 - 3*x^2 - 2*x^3 + x^4)/(1+x)/(x^2+1)/(x-1)^4, {x, 0, 40}], x] (* Vincenzo Librandi, Dec 18 2012 *)
PROG
(Magma) I:=[8, 24, 54, 102, 174, 270, 396]; [n le 7 select I[n] else 3*Self(n-1)-3*Self(n-2)+Self(n-3)+Self(n-4)-3*Self(n-5)+3*Self(n-6)-Self(n-7): n in [1..40]]; // Vincenzo Librandi, Dec 19 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Mar 22 2009
EXTENSIONS
More terms from R. J. Mathar, Sep 27 2009
STATUS
approved