# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a003990 Showing 1-1 of 1 %I A003990 #34 Apr 01 2018 18:10:19 %S A003990 1,2,2,3,2,3,4,6,6,4,5,4,3,4,5,6,10,12,12,10,6,7,6,15,4,15,6,7,8,14,6, %T A003990 20,20,6,14,8,9,8,21,12,5,12,21,8,9,10,18,24,28,30,30,28,24,18,10,11, %U A003990 10,9,8,35,6,35,8,9,10,11,12,22,30,36,40,42,42,40,36,30,22,12,13,12,33,20,45,24 %N A003990 Table of lcm(x,y), read along antidiagonals. %C A003990 A(x,x) = x on the diagonal. - _Reinhard Zumkeller_, Aug 05 2012 %H A003990 T. D. Noe, First 100 antidiagonals of array, flattened %H A003990 Kival Ngaokrajang, Illustration of pattern, where terms with least significant decimal digit equal to zero are colored. %H A003990 Index entries for sequences related to lcm's %e A003990 The symmetric array is lcm(x,y) = lcm(y,x): %e A003990 1 2 3 4 5 6 7 8 9 10 ... %e A003990 2 2 6 4 10 6 14 8 18 10 ... %e A003990 3 6 3 12 15 6 21 24 9 30 ... %e A003990 4 4 12 4 20 12 28 8 36 20 ... %e A003990 5 10 15 20 5 30 35 40 45 10 ... %e A003990 6 6 6 12 30 6 42 24 18 30 ... %e A003990 7 14 21 28 35 42 7 56 63 70 ... %e A003990 8 8 24 8 40 24 56 8 72 40 ... %e A003990 9 18 9 36 45 18 63 72 9 90 ... %e A003990 10 10 30 20 10 30 70 40 90 10 ... %t A003990 Table[ LCM[x-y, y], {x, 1, 14}, {y, 1, x-1}] // Flatten (* _Jean-François Alcover_, Aug 20 2013 *) %o A003990 (Haskell) %o A003990 a003990 x y = a003990_adiag x !! (y-1) %o A003990 a003990_adiag n = a003990_tabl !! (n-1) %o A003990 a003990_tabl = zipWith (zipWith lcm) a002260_tabl $ map reverse a002260_tabl %o A003990 -- _Reinhard Zumkeller_, Aug 05 2012 %o A003990 (PARI) A(x,y)=lcm(x,y) \\ _Charles R Greathouse IV_, Feb 06 2017 %Y A003990 Cf. A003989, A003991, A051173. %Y A003990 A(x, y) = A075174(A003986(A075173(x), A075173(y))) = A075176(A003986(A075175(x), A075175(y))). %Y A003990 Antidiagonal sums are in A006580. %Y A003990 Cf. A002260. %K A003990 tabl,nonn,easy,nice,look %O A003990 1,2 %A A003990 _Marc LeBrun_ # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE