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 A374072 Integers of the form x!*y!/(x! + y!) where x, y are positive integers. 0
 1, 3, 12, 20, 60, 360, 630, 2520, 4480, 20160, 36288, 181440, 1814400, 3326400, 19958400, 239500800, 444787200, 3113510400, 5811886080, 43589145600, 81729648000, 653837184000, 1302884352000, 10461394944000, 19760412672000, 177843714048000, 3201186852864000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The sequence contains A001710 when x=y. LINKS Table of n, a(n) for n=1..27. EXAMPLE 630 is in the sequence because with x=6 and y=7, 6!7!/(6!+7!) = 720*5040/(720+5040)=630. PROG (PARI) lista(nn) = select(x->(denominator(x)==1), setbinop((x, y)->x!*y!/(x! + y!), [1..nn])) \\ Michel Marcus, Jun 27 2024 CROSSREFS Cf. A001710. Sequence in context: A122576 A212760 A143268 * A193558 A256131 A080767 Adjacent sequences: A374069 A374070 A374071 * A374073 A374074 A374075 KEYWORD nonn AUTHOR Michel Lagneau, Jun 27 2024 STATUS approved

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Last modified September 15 02:47 EDT 2024. Contains 375930 sequences. (Running on oeis4.)