cp's OEIS Frontend

A127043 Primes p such that denominator of Sum_{k=1..p-1} 1/k^2 is not a square.

%I A127043 #7 Jan 03 2024 07:18:02
%S A127043 11,13,23,43,47,53,59,61,67,71,73,79,83,89,101,103,107,109,113,137,
%T A127043 139,149,151,157,163,167,173,179,181,191,193,197,199,251,257,263,269,
%U A127043 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
%N A127043 Primes p such that denominator of Sum_{k=1..p-1} 1/k^2 is not a square.
%H A127043 Robert Israel, <a href="/A127043/b127043.txt">Table of n, a(n) for n = 1..10000</a>
%p A127043 S:= 0: R:= NULL: count:= 0:
%p A127043 for k from 1 while count < 100 do
%p A127043   S:= S + 1/k^2;
%p A127043   if isprime(k+1) and not issqr(denom(S)) then
%p A127043        R:= R,k+1; count:= count+1;
%p A127043   fi
%p A127043 od:
%p A127043 R; # _Robert Israel_, Oct 25 2019
%t A127043 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
%Y A127043 Cf. A061002, A034602, A127029, A127042.
%K A127043 nonn
%O A127043 1,1
%A A127043 _Artur Jasinski_, Jan 03 2007
%E A127043 More terms from _Robert Israel_, Oct 25 2019