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A201250
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Integers k such that Sum_{i=1..k-1} (-1)^(i+1)*primepi((k-i+1)^2) = Sum_{i=1..k-1} (-1)^(i+1)*primepi((k-i)^2).
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0
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1, 3, 8, 16, 36, 38, 70, 108, 116, 148, 251, 280, 1964
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OFFSET
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1,2
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LINKS
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FORMULA
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A = Sum[{i=1 to n-1}(-1)^(i+1)*Pi[(n-i+1)^2];
B = Sum[{i=1 to n-1}(-1)^(i+1)*Pi[(n-i)^2];
Sequence is S_n = {index(A_n - B_n) such that A_n - B_n = 0}.
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EXAMPLE
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For k = 3, pi(3^2)-pi(2^2) = 2 = pi(2^2)-pi(1^2), so 3 is term.
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PROG
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(PARI) isok(k) = sum(i=1, k-1, (-1)^(i+1)*primepi((k-i+1)^2)) == sum(i=1, k-1, (-1)^(i+1)*primepi((k-i)^2)); \\ Michel Marcus, Aug 16 2022
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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