login
A105837
Numbers n such that n^2 = 11*m^2 + 11*m + 1.
1
1, 131, 529, 52139, 210541, 20751191, 83794789, 8258921879, 33350115481, 3287030156651, 13273262166649, 1308229743425219, 5282724992210821, 520672150853080511, 2102511273637740109, 207226207809782618159, 836794204182828352561
OFFSET
1,2
FORMULA
a(1)=1, a(2)=131, a(3)=398*a(1)+a(2), a(4)=398*a(2)+a(1), a(n)=398*a(n-2)-a(n-4) for n>4.
G.f.: x*(1+x)*(1+130*x+x^2)/((1-20*x+x^2)*(1+20*x+x^2)). [Bruno Berselli, Feb 21 2013]
MATHEMATICA
LinearRecurrence[{0, 398, 0, -1}, {1, 131, 529, 52139}, 17]
CROSSREFS
Cf. A105838 (associated m).
Sequence in context: A276255 A142555 A118507 * A142205 A142807 A103834
KEYWORD
nonn,easy
AUTHOR
Pierre CAMI, Apr 22 2005
EXTENSIONS
More terms from Bruno Berselli, Feb 21 2013
STATUS
approved