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A178671
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a(n) = 5^n - 5.
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3
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-4, 0, 20, 120, 620, 3120, 15620, 78120, 390620, 1953120, 9765620, 48828120, 244140620, 1220703120, 6103515620, 30517578120, 152587890620, 762939453120, 3814697265620, 19073486328120, 95367431640620, 476837158203120, 2384185791015620, 11920928955078120
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 5*a(n-1) + 20 with a(0) = -4.
G.f.: 4*(-1+6*x)/((1-5*x)*(1-x)).
a(n) = 4*A104891(n-1), n > 0. (End)
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EXAMPLE
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MATHEMATICA
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PROG
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(Magma) [5^n-5: n in [0..25]];
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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