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A175490 a(n) = Product_{k=1..n} b(k,n), where b(k,n) is the largest positive integer that, when written in binary, occurs as a substring in both binary k and binary n.

%I A175490 #14 Feb 05 2020 15:00:47
%S A175490 1,2,3,8,20,144,63,256,1152,1600,118800,995328,8424000,12192768,
%T A175490 178605,1048576,8912896,21233664,27572576256,13107200000,537600000,
%U A175490 2032335360000,30928035600000,760840571584512,13541327555788800
%N A175490 a(n) = Product_{k=1..n} b(k,n), where b(k,n) is the largest positive integer that, when written in binary, occurs as a substring in both binary k and binary n.
%C A175490 Row products of A175488. - _R. J. Mathar_, Sep 28 2010
%H A175490 Rémy Sigrist, <a href="/A175490/b175490.txt">Table of n, a(n) for n = 1..819</a>
%H A175490 Rémy Sigrist, <a href="/A175490/a175490.gp.txt">PARI program for A175490</a>
%p A175490 A175488 := proc(n,m) for a from m to 1 by -1 do abin := convert(a,base,2) ; nbin := convert(n,base,2) ; mbin := convert(m,base,2) ; if verify(abin,nbin,'sublist') and verify(abin,mbin,'sublist') then return a; end if; end do: end proc:
%p A175490 A175490 := proc(n) mul(A175488(n,m),m=1..n) ; end proc:
%p A175490 seq(A175490(n),n=1..30) ;
%p A175490 # _R. J. Mathar_, Sep 28 2010
%o A175490 (PARI) See Links section.
%Y A175490 Cf. A175488, A175489.
%K A175490 base,nonn
%O A175490 1,2
%A A175490 _Leroy Quet_, May 28 2010
%E A175490 More terms from _R. J. Mathar_, Sep 28 2010