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 A127043 Primes p such that denominator of Sum_{k=1..p-1} 1/k^2} is not a square. 7
 11, 13, 23, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 101, 103, 107, 109, 113, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE S:= 0: R:= NULL: count:= 0: for k from 1 while count < 100 do   S:= S + 1/k^2;   if isprime(k+1) and not issqr(denom(S)) then        R:= R, k+1; count:= count+1;   fi od: R; # Robert Israel, Oct 25 2019 MATHEMATICA a = {}; Do[If[Sqrt[Denominator[Sum[1/x^2, {x, 1, Prime[x] - 1}]]] == Floor[Sqrt[Denominator[Sum[1/x^2, {x, 1, Prime[x] - 1}]]]], 1, AppendTo[a, Prime[x]]], {x, 1, 50}]; a CROSSREFS Cf. A061002, A034602, A127029, A127042. Sequence in context: A072330 A097933 A166484 * A084952 A277048 A275598 Adjacent sequences:  A127040 A127041 A127042 * A127044 A127045 A127046 KEYWORD nonn AUTHOR Artur Jasinski, Jan 03 2007 EXTENSIONS More terms from Robert Israel, Oct 25 2019 STATUS approved

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Last modified February 26 18:29 EST 2020. Contains 332293 sequences. (Running on oeis4.)