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A163301
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a(n) = Sum_{x=n-th even nonprime..n-th odd nonprime} -x*(-1)^x.
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1
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1, 3, 5, 7, 8, 8, 10, 10, 11, 13, 14, 14, 15, 15, 17, 17, 18, 20, 20, 21, 22, 22, 23, 23, 23, 24, 26, 28, 29, 29, 29, 29, 29, 29, 30, 31, 31, 33, 33, 33, 33, 35, 35, 36, 36, 37, 38, 38, 39, 39, 41, 41, 41, 41, 43, 45, 45, 45, 45, 45, 46, 46, 46, 46, 46, 47, 49, 50, 50, 52, 52
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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a(1) = -0*(-1)^0 - 1*(-1)^1 = 0 + 1 = 1;
a(2) = -4*(-1)^4 - 5*(-1)^5 - 6*(-1)6 - 7*(-1)^7 - 8*(-1)^8 - 9*(-1)^9 = -4 + 5 - 6 + 7 - 8 + 9 = 3.
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MAPLE
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A163300 := proc(n) if n <= 2 then op(n, [0, 4]) ; else for a from procname(n-1)+2 by 2 do if not isprime(a) then return a; end if; end do; end if; end proc:
A014076 := proc(n) if n = 1 then 1; else for a from procname(n-1)+2 by 2 do if not isprime(a) then return a ; end if; end do: end if; end proc:
A001057 := proc(n) (1-(-1)^n*(2*n+1))/4; end proc:
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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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