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A178397
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Partial sums of round(7^n/10).
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1
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0, 1, 6, 40, 280, 1961, 13726, 96080, 672560, 4707921, 32955446, 230688120, 1614816840, 11303717881, 79126025166, 553882176160, 3877175233120, 27140226631841, 189981586422886, 1329871104960200, 9309097734721400
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = round((7*7^n-7)/60) = round((7*7^n+5)/60).
a(n) = floor((7*7^n+17)/60).
a(n) = ceiling((7*7^n-7)/60).
a(n) = a(n-4) + 40*7^(n-3), n > 3.
a(n) = 8*a(n-1) - 8*a(n-2) + 8*a(n-3) - 7*a(n-4), n > 3.
G.f.: -(2*x^2-x)/((x-1)*(7*x-1)*(x^2+1)).
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EXAMPLE
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a(4) = 0 + 1 + 5 + 34 + 240 = 280.
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MAPLE
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A178397 := proc(n) add( round(7^i/10), i=0..n) ; end proc:
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MATHEMATICA
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Accumulate[Floor[7^Range[0, 20]/10+1/2]] (* Harvey P. Dale, Aug 20 2011 *)
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PROG
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(PARI) a(n) = (7*7^n+17)\60; \\ Altug Alkan, Sep 21 2018
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CROSSREFS
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KEYWORD
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nonn,less
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AUTHOR
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STATUS
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approved
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