OFFSET
1,2
COMMENTS
Central terms of triangle A214661.
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
G.f.: x*(1+12*x+5*x^2)/(1-x)^3. - Bruno Berselli, Dec 10 2012
E.g.f.: -5 + (5 - 4*x + 9*x^2)*exp(x). - G. C. Greubel, Mar 08 2024
MATHEMATICA
Table[9n^2-13n+5, {n, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 15, 47}, 50] (* Harvey P. Dale, Nov 09 2019 *)
PROG
(Haskell)
a214675 n = (9 * n - 13) * n + 5
(PARI) a(n)=9*n^2-13*n+5 \\ Charles R Greathouse IV, Oct 07 2015
(Magma) [(3*n-2)^2-(n-1): n in [1..50]]; // G. C. Greubel, Mar 08 2024
(SageMath) [(3*n-2)^2-(n-1) for n in range(1, 51)] # G. C. Greubel, Mar 08 2024
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Reinhard Zumkeller, Jul 25 2012
STATUS
approved