login
A062919
"Reverse factorials": product of the digit reversals of the numbers 1 through n.
2
1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 362880, 3991680, 83825280, 2598583680, 106541930880, 5433638474880, 331451946967680, 23533088234705280, 1906180147011127680, 173462393378012618880
OFFSET
0,3
COMMENTS
How many trailing zeros are there in a(n)?
LINKS
FORMULA
a(n) = Product_{k=1..n} A004086(k). - Michel Marcus, Jun 28 2018
EXAMPLE
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.
MATHEMATICA
FoldList[Times, 1, Table[FromDigits[Reverse[IntegerDigits[n]]], {n, 20}]] (* Harvey P. Dale, Aug 20 2012 *)
PROG
(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
CROSSREFS
Sequence in context: A109834 A131451 A084012 * A319211 A276843 A273696
KEYWORD
base,nonn,easy
AUTHOR
Amarnath Murthy, Jul 02 2001
EXTENSIONS
More terms from Lior Manor and Larry Reeves (larryr(AT)acm.org), Jul 05 2001
STATUS
approved