# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/

Search: id:a137519
Showing 1-1 of 1

%I A137519 #11 Sep 22 2019 20:43:46
%S A137519 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 A137519 77,79,83,89,97,101,103,107,109,113,119,121,127,129,131,133,137,139,
%U A137519 143,149,151,157,159,161,163,167,169,173,179,181,187,191,193,197,199,203
%N A137519 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 A137519 Robert Israel, <a href="/A137519/b137519.txt">Table of n, a(n) for n = 1..10000</a>
%p A137519 N:= 100: # for a(1)..a(N)
%p A137519 A[1]:= 1: A[2]:= 2:
%p A137519 for n from 3 to N do
%p A137519   t:= (A[n-1]+1)*(A[n-2]+1);
%p A137519   for k from A[n-1]+1 do
%p A137519     if igcd(k,t)=1 then
%p A137519       A[n]:= k;
%p A137519       break
%p A137519     fi
%p A137519   od;
%p A137519 od:
%p A137519 [seq(A[i],i=1..N)]: # _Robert Israel_, Sep 22 2019
%t A137519 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 A137519 nonn
%O A137519 1,2
%A A137519 _Leroy Quet_, Apr 24 2008
%E A137519 More terms from _Stefan Steinerberger_, Apr 26 2008

# Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE