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A162938
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A 2-based alternate sum over the numbers from 0 to the n-th nonprime.
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2
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2, 5, 8, 11, 14, 25, 17, 20, 23, 40, 26, 29, 32, 55, 35, 38, 65, 41, 70, 44, 47, 50, 85, 53, 90, 56, 59, 100, 62, 65, 68, 115, 71, 74, 125, 77, 130, 80, 83, 140, 86, 145, 89, 92, 95, 160, 98, 165, 101, 104, 175, 107, 110, 113, 190, 116, 195, 119, 122, 205, 125, 128, 215
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OFFSET
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1,1
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COMMENTS
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Define a 2-based sum S(n) = Sum_{i=0..n} (2 - (-1)^i*i) = 2*n - (-1)^n*A152832(n).
a(n) is this sum evaluated at A141468(n).
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 2 - 0*(-1)^0 = 2.
a(2) = 2 - 0*(-1)^0 + 2 - 1*(-1)^1 = 2 + 3 = 5.
a(3) = 2 - 0*(-1)^0 + 2 - 1*(-1)^1 + 2 - 2*(-1)^2 + 2 - 3*(-1)^3 + 2 - 4*(-1)^4 = 2 + 3 + 0 + 5 - 2 = 8.
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MAPLE
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A152832 := proc(n) option remember; if n = 0 then -2; else n-procname(n-1) ; fi; end:
A141468 := proc(n) option remember ; local a; if n <=2 then n-1; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a); fi; od: fi; end:
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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