OFFSET
0,1
COMMENTS
Diagonal of triangular spiral in A051682. - Paul Barry, Mar 15 2003
Ehrhart polynomial of open quadrilateral with vertices (0,2),(2,3),(3,1),(2,0). - Michael Somos, Jul 22 2006
LINKS
Harry J. Smith, Table of n, a(n) for n = 0..1000
Milan Janjic, Two Enumerative Functions
National Security Agency, Intrigued? (advertisement), Notices of the Amer. Math. Soc., vol. 49 (2002), p. 216.
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = 3*C(n, 0)+11*C(n, 1)+9*C(n, 2); binomial transform of (3, 11, 9, 0, 0, 0, .....). G.f.:(3+5*x+x^2)/(1-x)^3. - Paul Barry, Mar 15 2003
A064225(n) = a(-1-n). - Michael Somos, Jul 22 2006
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Wesley Ivan Hurt, Apr 16 2023
MAPLE
MATHEMATICA
Table[(9 n^2 + 13 n + 6)/2, {n, 0, 50}] (* Wesley Ivan Hurt, May 08 2014 *)
LinearRecurrence[{3, -3, 1}, {3, 14, 34}, 50] (* Vincenzo Librandi, Jul 19 2015 *)
PROG
(PARI) {a(n) = 3 + n * (9*n + 13) / 2}; /* Michael Somos, Jul 22 2006 */
(PARI) for (n=0, 1000, write("b064226.txt", n, " ", 3 + n*(9*n + 13)/2) ) \\ Harry J. Smith, Sep 10 2009
(Magma) I:=[3, 14, 34]; [n le 3 select I[n] else 3*Self(n-1) - 3*Self(n-2) + Self(n-3): n in [1..50]]; // Vincenzo Librandi, Jul 19 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Sep 22 2001
STATUS
approved