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A325912
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a(n) = (-1)^n * Sum_{k=0..n} (-1)^k*2^(2^k).
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2
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2, 2, 14, 242, 65294, 4294902002, 18446744069414649614, 340282366920938463444927863362353561842, 115792089237316195423570985008687907852929702298719625576012656144550776078094
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OFFSET
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0,1
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LINKS
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FORMULA
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EXAMPLE
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a(0) = 2^1 = 2.
a(1) = 2^2 - 2^1 = 2.
a(2) = 2^4 - 2^2 + 2^1 = 14.
a(3) = 2^8 - 2^4 + 2^2 - 2^1 = 242.
a(4) = 2^16 - 2^8 + 2^4 - 2^2 + 2^1 = 65294.
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MATHEMATICA
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a[n_] := (-1)^n * Sum[(-1)^k * 2^(2^k), {k, 0, n}]; Array[a, 9, 0] (* Amiram Eldar, May 07 2021 *)
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PROG
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(PARI) {a(n) = (-1)^n*sum(k=0, n, (-1)^k*2^2^k)}
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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