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A003990 Table of lcm(x,y), read along antidiagonals. 29
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, 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, 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 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
A(x,x) = x on the diagonal. - Reinhard Zumkeller, Aug 05 2012
LINKS
Kival Ngaokrajang, Illustration of pattern, where terms with least significant decimal digit equal to zero are colored.
EXAMPLE
The symmetric array is lcm(x,y) = lcm(y,x):
1 2 3 4 5 6 7 8 9 10 ...
2 2 6 4 10 6 14 8 18 10 ...
3 6 3 12 15 6 21 24 9 30 ...
4 4 12 4 20 12 28 8 36 20 ...
5 10 15 20 5 30 35 40 45 10 ...
6 6 6 12 30 6 42 24 18 30 ...
7 14 21 28 35 42 7 56 63 70 ...
8 8 24 8 40 24 56 8 72 40 ...
9 18 9 36 45 18 63 72 9 90 ...
10 10 30 20 10 30 70 40 90 10 ...
MATHEMATICA
Table[ LCM[x-y, y], {x, 1, 14}, {y, 1, x-1}] // Flatten (* Jean-François Alcover, Aug 20 2013 *)
PROG
(Haskell)
a003990 x y = a003990_adiag x !! (y-1)
a003990_adiag n = a003990_tabl !! (n-1)
a003990_tabl = zipWith (zipWith lcm) a002260_tabl $ map reverse a002260_tabl
-- Reinhard Zumkeller, Aug 05 2012
(PARI) A(x, y)=lcm(x, y) \\ Charles R Greathouse IV, Feb 06 2017
CROSSREFS
A(x, y) = A075174(A003986(A075173(x), A075173(y))) = A075176(A003986(A075175(x), A075175(y))).
Antidiagonal sums are in A006580.
Cf. A002260.
Sequence in context: A045772 A294977 A091256 * A287958 A308630 A059896
KEYWORD
tabl,nonn,easy,nice,look
AUTHOR
STATUS
approved

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Last modified March 19 03:33 EDT 2024. Contains 370952 sequences. (Running on oeis4.)