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A024049
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a(n) = 5^n - 1.
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35
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0, 4, 24, 124, 624, 3124, 15624, 78124, 390624, 1953124, 9765624, 48828124, 244140624, 1220703124, 6103515624, 30517578124, 152587890624, 762939453124, 3814697265624, 19073486328124, 95367431640624
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OFFSET
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0,2
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COMMENTS
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Numbers whose base 5 representation is 44444.......4. - Zerinvary Lajos, Feb 03 2007
For n > 0, a(n) is the sum of divisors of 3*5^(n-1). - Patrick J. McNab, May 27 2017
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LINKS
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FORMULA
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a(n) = Sum_{i=1..n} 4^i*binomial(n,n-i) for n>0, a(0)=0. - Bruno Berselli, Nov 11 2015
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EXAMPLE
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For n = 5, a(5) = 4*5 + 16*10 + 64*10 + 256*5 + 1024*1 = 3124. - Bruno Berselli, Nov 11 2015
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MATHEMATICA
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LinearRecurrence[{6, -5}, {0, 4}, 30] (* Harvey P. Dale, Apr 06 2019 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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