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A133284
Indices of the 12-gonal numbers which are also centered 12-gonal number or numbers X such that 30*X^2-24*X+3 is a square.
0
1, 13, 277, 6073, 133321, 2926981, 64260253, 1410798577, 30973308433, 680001986941, 14929070404261, 327759546906793, 7195780961545177, 157979421607087093, 3468351494394370861, 76145753455069071841
OFFSET
1,2
FORMULA
a(n+2)=22*a(n+1)-a(n)-8 ; a(n+1)=11*a(n)-4+2*(30*a(n)^2-24*a(n)+3)^0.5
G.f.: x(1-10x+x^2)/((1-x)(1-22x+x^2)). [From R. J. Mathar, Oct 30 2008]
MATHEMATICA
Rest[CoefficientList[Series[x (1-10x+x^2)/((1-x)(1-22x+x^2)), {x, 0, 20}], x]] (* or *) LinearRecurrence[{23, -23, 1}, {1, 13, 277}, 20] (* Harvey P. Dale, Nov 07 2019 *)
CROSSREFS
Sequence in context: A295096 A295550 A320336 * A012570 A256044 A160294
KEYWORD
nonn
AUTHOR
Richard Choulet, Oct 16 2007
EXTENSIONS
More terms from Paolo P. Lava, Aug 06 2008
STATUS
approved