OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3); a(1)=390, a(2)=750, a(3)=1230. - Harvey P. Dale, Apr 06 2012
Sum_{n>=1} 1/a(n) = (Pi/60)*tanh(Pi/2) - 1/25. - Amiram Eldar, Jan 27 2022
MATHEMATICA
Table[30 (2 n^2 + 6 n + 5), {n, 1, 100}] (* Vladimir Joseph Stephan Orlovsky, Jun 19 2011 *)
LinearRecurrence[{3, -3, 1}, {390, 750, 1230}, 40] (* Harvey P. Dale, Apr 06 2012 *)
PROG
(Magma) [30*(2*n^2 + 6*n + 5): n in [1..40]]; // Vincenzo Librandi, Nov 23 2011
(PARI) a(n)=60*n^2+180*n+150 \\ Charles R Greathouse IV, Nov 23 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eli McGowan (ejmcgowa(AT)mail.lakeheadu.ca), Apr 11 2002
STATUS
approved