A062919 "Reverse factorials": product of the digit reversals of the numbers 1 through n.

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

Harry J. Smith, Table of n, a(n) for n = 0..100

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

Cf. A000142, A004086.

Sequence in context: A109834 A131451 A084012 * A319211 A276843 A273696

Adjacent sequences: A062916 A062917 A062918 * A062920 A062921 A062922

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