|
| |
| |
|
|
|
30, 105, 230, 405, 630, 905, 1230, 1605, 2030, 2505, 3030, 3605, 4230, 4905, 5630, 6405, 7230, 8105, 9030, 10005, 11030, 12105, 13230, 14405, 15630, 16905, 18230, 19605, 21030, 22505, 24030, 25605, 27230, 28905, 30630, 32405, 34230, 36105
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
The identity (10*n^2+1)^2-(25*n^2+5) *(2*n)^2=1 can be written as A158187(n)^2-a(n)*A005843(n)^2=1.
|
|
|
LINKS
|
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
|
|
|
FORMULA
|
a(n) = 3*a(n-1) -3*a(n-2) +a(n-3).
G.f: 5*x*(6+3*x+x^2)/(1-x)^3.
|
|
|
MATHEMATICA
|
Table[25n^2+5, {n, 50}]
|
|
|
PROG
|
(MAGMA) I:=[30, 105, 230]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+Self(n-3): n in [1..50]];
(PARI) a(n) = 25*n^2 + 5.
|
|
|
CROSSREFS
|
Cf. A005843, A158187.
Sequence in context: A043998 A101056 A081370 * A046301 A193873 A205836
Adjacent sequences: A158442 A158443 A158444 * A158446 A158447 A158448
|
|
|
KEYWORD
|
nonn,easy
|
|
|
AUTHOR
|
Vincenzo Librandi, Mar 19 2009
|
|
|
STATUS
|
approved
|
| |
|
|
