|
%I #16 Jun 28 2018 04:45:31
%S 1,1,2,6,24,120,720,5040,40320,362880,362880,3991680,83825280,
%T 2598583680,106541930880,5433638474880,331451946967680,
%U 23533088234705280,1906180147011127680,173462393378012618880
%N "Reverse factorials": product of the digit reversals of the numbers 1 through n.
%C How many trailing zeros are there in a(n)?
%H Harry J. Smith, <a href="/A062919/b062919.txt">Table of n, a(n) for n = 0..100</a>
%F a(n) = Product_{k=1..n} A004086(k). - _Michel Marcus_, Jun 28 2018
%e a(11) = 3991680 = 1*2*3*4*5*6*7*8*9*R(10)*R(11) = 1*2*3*4*5*6*7*8*9*1*11.
%t FoldList[Times,1,Table[FromDigits[Reverse[IntegerDigits[n]]],{n,20}]] (* _Harvey P. Dale_, Aug 20 2012 *)
%o (PARI) Rev(x)= { local(d); r=0; while (x>0, d=x-10*(x\10); x\=10; r=r*10 + d); return(r) } { for (n=0, 100, if (n, a*=Rev(n), a=1); write("b062919.txt", n, " ", a) ) } \\ _Harry J. Smith_, Aug 13 2009
%Y Cf. A000142, A004086.
%K base,nonn,easy
%O 0,3
%A _Amarnath Murthy_, Jul 02 2001
%E More terms from _Lior Manor_ and Larry Reeves (larryr(AT)acm.org), Jul 05 2001
|
