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A186828
Diagonal sums of number triangle A186826.
1
1, 1, 4, 14, 57, 247, 1124, 5296, 25621, 126529, 635264, 3232886, 16638821, 86456767, 452927448, 2389672752, 12686560409, 67721774737, 363268546892, 1957131383342, 10585610149121, 57458399978455, 312890905815900, 1708883398754176, 9358483855106829, 51378142520487281, 282714583026982504
OFFSET
0,3
FORMULA
G.f.: (1+x-3x^2+x^3-(1+x^2)*sqrt(1-6x+x^2))/(4x(1-x+x^2+x^3)).
Conjecture: (n+1)*a(n) +(-7*n+2)*a(n-1) +(9*n-7)*a(n-2) +(-13*n+36)*a(n-3) +(3*n-35)*a(n-4) +(-5*n+28)*a(n-5) +(-5*n+21)*a(n-6) +(n-6)*a(n-7)=0. - R. J. Mathar, Feb 13 2015
MATHEMATICA
CoefficientList[Series[(1+x-3x^2+x^3-(1+x^2)Sqrt[1-6x+x^2])/(4x(1-x+ x^2+ x^3)), {x, 0, 30}], x] (* Harvey P. Dale, Aug 23 2011 *)
CROSSREFS
Sequence in context: A002735 A026652 A269134 * A151489 A325929 A134826
KEYWORD
nonn,easy
AUTHOR
Paul Barry, Feb 27 2011
STATUS
approved