%I
%S 1,2,4,6,8,10,12,14,18,22,26,28,30,32,36,40,44,48,50,54,58,60,62,66,
%T 76,78,82,84,94,96,98,100,102,104,114,116,120,126,132,136,138,140,144,
%U 150,154,158,162,166,170,176,184,188,190,198,202,204,208,210,212,216,220
%N Positive integers that cannot be represented in the form n=5ab+a+b for any choice of nonzero integers a and b (positive or negative).
%C All terms except 1 are even.  _Robert Israel_, Apr 07 2019
%H Robert Israel, <a href="/A058218/b058218.txt">Table of n, a(n) for n = 1..10000</a>
%H Maria Suzuki, <a href="http://www.jstor.org/stable/2589378">Related to Alternative Formulations of the Twin Prime Problem</a>, American Math. Monthly, 107 (2000) pp. 5556.
%p filter:= proc(n)
%p nops(select(t > t mod 5 = 1 or t mod 5 = 4, numtheory:divisors(5*n+1))) = 2
%p and nops(select(t > t mod 5 = 4, numtheory:divisors(5*n1)))=1
%p end proc:
%p select(filter, [$1..1000]); # _Robert Israel_, Apr 07 2019
%t filterQ[n_] := Length[Select[Divisors[5 n + 1], Mod[#, 5] == 1  Mod[#, 5] == 4&]] == 2 && Length[Select[Divisors[5 n  1], Mod[#, 5] == 4&]] == 1;
%t Select[Range[1000], filterQ] (* _JeanFrançois Alcover_, Aug 16 2020, after _Robert Israel_ *)
%Y A002822 results if the coefficient 5 in the definition above is replaced by 6.
%Y Includes 2*A124518.
%K nonn
%O 1,2
%A _John W. Layman_, Nov 30 2000
