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A051801 Product of the nonzero digits of n. 24
1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 2, 2, 4, 6, 8, 10, 12, 14, 16, 18, 3, 3, 6, 9, 12, 15, 18, 21, 24, 27, 4, 4, 8, 12, 16, 20, 24, 28, 32, 36, 5, 5, 10, 15, 20, 25, 30, 35, 40, 45, 6, 6, 12, 18, 24, 30, 36, 42, 48, 54, 7, 7, 14, 21 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Zak Seidov and Michael De Vlieger, Table of n, a(n) for n = 0..10000 (First 1000 terms from Zak Seidov)

Index entries for Colombian or self numbers and related sequences

FORMULA

a(n) = if n=0 then 1 else a([n/10]) * (n mod 10 + 0^(n mod 10)). [Reinhard Zumkeller, Oct 13 2009]

EXAMPLE

a(0) = 1 since an empty product is 1 by convention. a(120) = 1*2 = 2.

MAPLE

A051801 := proc(n) local d, j: d:=convert(n, base, 10): return mul(`if`(d[j]=0, 1, d[j]), j=1..nops(d)): end: seq(A051801(n), n=0..100); # Nathaniel Johnston, May 04 2011

MATHEMATICA

(Times@@Cases[IntegerDigits[#], Except[0]])&/@Range[0, 80] (* Harvey P. Dale, Jun 20 2011 *)

PROG

(Haskell)

a051801 0 = 1

a051801 n = (a051801 n') * (m + 0 ^ m) where (n', m) = divMod n 10

-- Reinhard Zumkeller, Nov 23 2011

(PARI) a(n)=my(v=select(k->k>1, digits(n))); prod(i=1, #v, v[i]) \\ Charles R Greathouse IV, Nov 20 2012

(Python)

from operator import mul

from functools import reduce

def A051801(n):

....return reduce(mul, (int(d) for d in str(n) if d != '0')) if n > 0 else 1

# Chai Wah Wu, Aug 23 2014

CROSSREFS

Basis for A051802.

Sequence in context: A067456 A052429 A051802 * A071205 A066750 A217928

Adjacent sequences:  A051798 A051799 A051800 * A051802 A051803 A051804

KEYWORD

nonn,easy,base,nice

AUTHOR

Dan Hoey, Dec 09 1999

STATUS

approved

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Last modified October 22 06:02 EDT 2018. Contains 316432 sequences. (Running on oeis4.)