This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A051173 #48 Mar 24 2025 19:45:47
%S A051173 1,2,2,3,6,3,4,4,12,4,5,10,15,20,5,6,6,6,12,30,6,7,14,21,28,35,42,7,8,
%T A051173 8,24,8,40,24,56,8,9,18,9,36,45,18,63,72,9,10,10,30,20,10,30,70,40,90,
%U A051173 10,11,22,33,44,55,66,77,88,99,110,11,12,12,12,12,60,12,84,24,36,60,132,12
%N A051173 Triangle read by rows: T(n, k) = lcm(n, k).
%H A051173 Reinhard Zumkeller, <a href="/A051173/b051173.txt">Rows n = 1..120 of triangle, flattened</a>
%H A051173 Keith Bourque and Steve Ligh, <a href="https://doi.org/10.1016/0024-3795(93)00154-R">Matrices associated with multiplicative functions</a>, Linear Algebra and its Applications 216 (1995) 267-275.
%H A051173 Shaofang Hong and Raphael Loewy, <a href="https://doi.org/10.1017/S0017089504001995">Asymptotic behavior of eigenvalues of greatest common divisor matrices</a>, Glasgow Mathematical Journal, Vol. 46, No. 3 (2004) 551-569.
%H A051173 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LeastCommonMultiple.html">Least Common Multiple</a>
%H A051173 Wikipedia, <a href="https://en.wikipedia.org/wiki/Least_common_multiple">Least Common Multiple</a>
%H A051173 <a href="/index/Lc#lcm">Index entries for sequences related to lcm's</a>
%F A051173 T(n, 1) = T(n, n) = n. T(n, 2) = A109043(n). - _R. J. Mathar_, Apr 07 2011
%F A051173 T(n, k) = A075362(n, k)/A050873(n, k), 1 <= k <= n. - _Reinhard Zumkeller_, Apr 25 2011
%F A051173 T(n, k) = A051537(n, k) * A050873(n, k). - _Reinhard Zumkeller_, Jul 07 2013
%e A051173 Triangle begins (for the full array see A109042):
%e A051173 [1] 1;
%e A051173 [2] 2, 2;
%e A051173 [3] 3, 6, 3;
%e A051173 [4] 4, 4, 12, 4;
%e A051173 [5] 5, 10, 15, 20, 5;
%e A051173 [6] 6, 6, 6, 12, 30, 6;
%e A051173 [7] 7, 14, 21, 28, 35, 42, 7;
%e A051173 [8] 8, 8, 24, 8, 40, 24, 56, 8;
%p A051173 A051173 := proc(u,v) ilcm(u,v) ; end proc: # _R. J. Mathar_, Apr 07 2011
%t A051173 Table[LCM[n, k], {n, 1, 12}, {k, 1, n}] // Flatten (* _Jean-François Alcover_, Jan 30 2018 *)
%o A051173 (Haskell)
%o A051173 a051173 = lcm
%o A051173 a051173_row n = a051173_tabl !! (n-1)
%o A051173 a051173_tabl = map (\x -> map (lcm x) [1..x]) [1..]
%o A051173 -- _Reinhard Zumkeller_, Aug 13 2013, Jul 07 2013
%o A051173 (PARI) T(n,k) = lcm(n,k);
%o A051173 tabl(nn) = for (n=1, nn, for (k=1, n, print1(T(n,k), ", ")); print;) \\ _Michel Marcus_, Jul 10 2017
%Y A051173 Cf. A109043 (column 2), A051193 (row sums), A000384 (central terms).
%Y A051173 Cf. A109042 (variant), A003990, A002260, A075362, A051537, A050873.
%K A051173 nonn,easy,tabl
%O A051173 1,2
%A A051173 _Clark Kimberling_