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%I #11 Sep 22 2019 20:43:46
%S 1,2,5,7,11,13,17,19,23,29,31,37,39,41,43,47,49,53,59,61,67,69,71,73,
%T 77,79,83,89,97,101,103,107,109,113,119,121,127,129,131,133,137,139,
%U 143,149,151,157,159,161,163,167,169,173,179,181,187,191,193,197,199,203
%N a(1)=1. a(2)=2. For n>=3, a(n) = the smallest integer > a(n-1) that is coprime to (a(n-1)+1)*(a(n-2)+1).
%H Robert Israel, <a href="/A137519/b137519.txt">Table of n, a(n) for n = 1..10000</a>
%p N:= 100: # for a(1)..a(N)
%p A[1]:= 1: A[2]:= 2:
%p for n from 3 to N do
%p t:= (A[n-1]+1)*(A[n-2]+1);
%p for k from A[n-1]+1 do
%p if igcd(k,t)=1 then
%p A[n]:= k;
%p break
%p fi
%p od;
%p od:
%p [seq(A[i],i=1..N)]: # _Robert Israel_, Sep 22 2019
%t a = {1, 2}; For[n = 3, n < 80, n++, i = a[[ -1]] + 1; While[GCD[(a[[ -1]] + 1)*(a[[ -2]] + 1), i] > 1, i++ ]; AppendTo[a, i]]; a (* _Stefan Steinerberger_, Apr 26 2008 *)
%K nonn
%O 1,2
%A _Leroy Quet_, Apr 24 2008
%E More terms from _Stefan Steinerberger_, Apr 26 2008
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