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A257971
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First differences of A006921.
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3
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0, 2, -1, 5, -2, 8, -5, 21, -8, 34, -21, 81, -34, 128, -81, 337, -128, 546, -337, 1301, -546, 2056, -1301, 5381, -2056, 8706, -5381, 20737, -8706, 32768, -20737, 86273, -32768, 139778, -86273, 333061, -139778, 526344, -333061, 1377557, -526344, 2228770
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OFFSET
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0,2
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LINKS
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FORMULA
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a(2*n+4) = - a(2*n+1).
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PROG
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(Haskell)
a257971 n = a257971_list !! n
a257971_list = zipWith (-) (tail a006921_list) a006921_list
(Python)
def A257971(n): return sum(int(not r & ~(n+2-r))*2**(n//2+1-r) for r in range(n//2+2)) if n & 1 else -sum(int(not r & ~(n-1-r))*2**(n//2-1-r) for r in range(n//2)) # Chai Wah Wu, Jun 20 2022
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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