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A020972
Expansion of 1/((1-7*x)*(1-9*x)*(1-12*x)).
1
1, 28, 529, 8428, 122257, 1673980, 22067473, 283450636, 3574941073, 44501447452, 548719235857, 6718924954924, 81849587868049, 993294339107644, 12020103854584081, 145151139884150092, 1750035954202640785
OFFSET
0,2
FORMULA
a(n) = 28*a(n-1) - 255*a(n-2) + 756*a(n-3), n>=3. - Vincenzo Librandi, Mar 15 2011
a(n) = 21*a(n-1) - 108*a(n-2) + 7^n, a(0)=1, a(1)=28. - Vincenzo Librandi, Mar 15 2011
a(n) = (2*12^(n+2) - 5*9^(n+2) + 3*7^(n+2))/30. - Yahia Kahloune, Jun 30 2013
MATHEMATICA
CoefficientList[Series[1/((1-7x)(1-9x)(1-12x)), {x, 0, 50}], x] (* G. C. Greubel, May 31 2018 *)
LinearRecurrence[{28, -255, 756}, {1, 28, 529}, 20] (* Harvey P. Dale, Oct 08 2020 *)
PROG
(PARI) x='x+O('x^50); Vec(1/((1-7*x)*(1-9*x)*(1-12*x))) \\ G. C. Greubel, May 31 2018
(Magma) m:=50; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-7*x)*(1-9*x)*(1-12*x)))); // G. C. Greubel, May 31 2018
CROSSREFS
Sequence in context: A020977 A020973 A023947 * A025957 A020758 A022000
KEYWORD
nonn
STATUS
approved