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%I #10 Aug 19 2024 09:15:58
%S 1,1,1,1,1,1,1,1,1,3628800,1,0,0,0,0,0,0,0,0,1216451004088320000,
%T 106661318400,1,0,0,0,0,0,0,0,44208809968698509772718080000000,
%U 1320509264105545113600000,10178348544000,1,0,0,0,0,0,0
%N a(n) = floor(n!/R(n)!), where R(n) = digit reversal of n (A004086).
%C If n < R(n) then a(n) = 0.
%C If n = R(n) then n is a palindrome and a(n) = 1.
%C If n > R(n) then n!/R(n)! is an integer.
%e a(21) = 21! / 12! = 51090942171709440000/479001600 = 106661318400.
%o (PARI) a(n) = n!\fromdigits(Vecrev(digits(n)))!; \\ _Michel Marcus_, Aug 19 2024
%Y Cf. A004086.
%K base,easy,nonn
%O 1,10
%A _Amarnath Murthy_, Feb 24 2002