|
|
A145123
|
|
Numbers n such that there exists x in N : (x+1)^3-x^3=19*n^2.
|
|
4
|
|
|
1, 301, 90901, 27451801, 8290353001, 2503659154501, 756096774306301, 228338722181348401, 68957538001992910801, 20824948137879677713501, 6289065380101660676566501, 1899276919842563644645369801
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
a(n+2) = 302*a(n+1)-a(n).
G.f.: -x*(-1+x) / ( 1-302*x+x^2 ). - R. J. Mathar, Nov 27 2011
|
|
EXAMPLE
|
a(1)=1 because 3^3-2^3=19*1.
|
|
MATHEMATICA
|
CoefficientList[Series[(1 - x)/(1 - 302 x + x^2), {x, 0, 20}], x] (* Vincenzo Librandi, Oct 18 2014 *)
|
|
PROG
|
(PARI) Vec(-x*(-1+x)/(1-302*x+x^2) + O(x^30)) \\ Colin Barker, Oct 18 2014
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|