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A274349 Products of two distinct Lucas numbers (2,3,4,7,11,18,...).

%I A274349 #14 Jan 01 2021 11:38:25
%S A274349 6,8,12,14,21,22,28,33,36,44,54,58,72,77,87,94,116,126,141,152,188,
%T A274349 198,203,228,246,304,319,329,369,398,492,517,522,532,597,644,796,836,
%U A274349 846,861,966,1042,1288,1353,1363,1368,1393,1563,1686,2084,2189,2204,2214
%N A274349 Products of two distinct Lucas numbers (2,3,4,7,11,18,...).
%H A274349 Robert Israel, <a href="/A274349/b274349.txt">Table of n, a(n) for n = 1..10000</a>
%e A274349 6 = 2*3, 44 = 4*11.
%p A274349 N:= 10000: # for terms <= N
%p A274349 L:= gfun:-rectoproc({f(n)=f(n-1)+f(n-2),f(0)=2,f(1)=1},f(n),remember):
%p A274349 S:= {}:
%p A274349 for i from 2 do
%p A274349   u:= L(i);
%p A274349   if u > N then break fi;
%p A274349   for j from 0 to i-1 do
%p A274349     if j = 1 then next fi;
%p A274349     v:= u*L(j);
%p A274349     if v > N then break fi;
%p A274349     S:= S union {v};
%p A274349 od od:
%p A274349 sort(convert(S,list)); # _Robert Israel_, Jan 01 2021
%t A274349 z = 100; f[n_] := LucasL[n]; f[1] = 2 ;
%t A274349 Take[Sort[Flatten[Table[f[u] f[v], {u, 1, z}, {v, 1, u - 1}]]], z]
%t A274349 Take[Times@@@Subsets[Join[{2},LucasL[Range[2,20]]],{2}]//Union,60] (* _Harvey P. Dale_, Aug 13 2019 *)
%Y A274349 Cf. A000032, A274348, A274347, A271354.
%K A274349 nonn,easy
%O A274349 1,1
%A A274349 _Clark Kimberling_, Jun 18 2016