cp's OEIS Frontend

A110975 Numbers n such that 2*prime(n) - prime(n+1) is a square.

%I A110975 #12 Mar 02 2020 16:25:30
%S A110975 1,2,5,6,11,24,49,50,73,87,182,183,202,203,307,309,379,458,459,520,
%T A110975 677,961,1001,1475,1618,1619,1769,2089,2427,2428,3303,3378,4090,4397,
%U A110975 4944,5444,5969,6496,6497,7653,8557,8871,8873,9091,9526,10524,11580,11824
%N A110975 Numbers n such that 2*prime(n) - prime(n+1) is a square.
%H A110975 Robert Israel, <a href="/A110975/b110975.txt">Table of n, a(n) for n = 1..1000</a>
%p A110975 Res:= NULL:  p:= 2; count:= 0:
%p A110975 for n from 1 while count < 100 do
%p A110975   q:= p; p:= nextprime(p);
%p A110975   if issqr(2*q-p) then count:= count+1; Res:= Res, n; fi
%p A110975 od:
%p A110975 Res; # _Robert Israel_, Mar 02 2020
%t A110975 Select[Range[12000], IntegerQ[(2Prime[ # ] - Prime[ # + 1])^(1/2)] &] (* _Ray Chandler_, Oct 07 2005 *)
%t A110975 Position[2#[[1]]-#[[2]]&/@Partition[Prime[Range[12000]],2,1],_?(IntegerQ[ Sqrt[#]]&)]//Flatten (* _Harvey P. Dale_, Apr 30 2019 *)
%Y A110975 Cf. A110970.
%K A110975 nonn
%O A110975 1,2
%A A110975 _Giovanni Teofilatto_, Sep 28 2005
%E A110975 Corrected and extended by _Ray Chandler_, Oct 07 2005