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A201250 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). 0
1, 3, 8, 16, 36, 38, 70, 108, 116, 148, 251, 280, 1964 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
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}.
EXAMPLE
For k = 3, pi(3^2)-pi(2^2) = 2 = pi(2^2)-pi(1^2), so 3 is term.
PROG
(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
CROSSREFS
Sequence in context: A024623 A337118 A344509 * A196373 A027291 A048952
KEYWORD
nonn,more
AUTHOR
Daniel Tisdale, Nov 28 2011
EXTENSIONS
New name and a(13) from Michel Marcus, Aug 16 2022
STATUS
approved

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Last modified March 29 06:34 EDT 2024. Contains 371265 sequences. (Running on oeis4.)