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A162886
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Even numbers in an alternating 1-based sum up to some odd nonprime.
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1
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24, 42, 54, 60, 78, 84, 96, 114, 132, 138, 144, 150, 168, 174, 180, 186, 204, 216, 222, 234, 240, 258, 264, 276, 282, 294, 306, 312, 324, 330, 348, 354, 366, 372, 384, 390, 402, 414, 420, 432, 438, 444, 450, 456, 474, 480, 486, 492, 504, 510, 516, 528, 534, 546, 558, 564
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OFFSET
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1,1
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COMMENTS
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Define an alternating sum S(n) = Sum_{k=0..n} (1-(-1)^k*k) = A064455(n+1).
The sequence contains this sum evaluated for an upper limit of the odd nonprimes where the sum is even.
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LINKS
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EXAMPLE
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S(n) evaluated at n=1, 9, 15, 21, ... (taken from A014076) is 3, 15, 24, 33, 42, 51, etc., where only the even values (i.e., 24, 42, etc.) join the sequence.
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MAPLE
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A014076 := proc(n) option remember ; if n = 1 then 1; else for a from procname(n-1)+2 by 2 do if not isprime(a) then RETURN(a) ; fi; od: fi; end:
for n from 1 to 200 do if S(n) mod 2 = 0 then printf("%d, ", S(n)) ; fi; od: # R. J. Mathar, Jul 21 2009
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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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EXTENSIONS
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STATUS
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approved
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