OFFSET
0,2
COMMENTS
Sequence found by reading the line from 0, in the direction 0, 10,..., in the square spiral whose vertices are the generalized dodecagonal numbers A195162. - Omar E. Pol, Sep 18 2011
LINKS
Ivan Panchenko, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = a(n-1) +40*n -30 (with a(0)=0). - Vincenzo Librandi, Dec 14 2010
From G. C. Greubel, May 30 2024: (Start)
G.f.: 10*x*(1 + 3*x)/(1-x)^3.
E.g.f.: 10*x*(1 + 2*x)*exp(x). (End)
MATHEMATICA
10*Binomial[2*Range[0, 40], 2] (* G. C. Greubel, May 30 2024 *)
PROG
(PARI) a(n)=10*n*(2*n-1) \\ Charles R Greathouse IV, Jun 17 2017
(Magma) [10*n*(2*n-1): n in [0..40]]; // G. C. Greubel, May 30 2024
(SageMath) [10*n*(2*n-1) for n in range(41)] # G. C. Greubel, May 30 2024
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Jan 01 2009
STATUS
approved