A171765 - OEIS

%I #9 Jan 11 2020 06:45:04

%S 0,0,0,0,0,0,0,0,0,0,0,1,2,3,4,5,6,7,8,9,0,2,4,6,8,10,12,14,16,18,0,3,

%T 6,9,12,15,18,21,24,27,0,4,8,12,16,20,24,28,32,36,0,5,10,15,20,25,30,

%U 35,40,45,0,6,12,18,24,30,36,42,48,54,0,7,14,21,28,35,42,49,56,63,0,8,16,24,32,40,48,56,64,72,0,9,18,27,36,45,54,63,72,81,0,0,0,0,0,0,0,0,0,0,0

%N a(n) = 0 if n <= 10; for n >= 11, a(n) = product of digits of n.

%p A171765 := proc(n)

%p     if n<= 10 then

%p         0;

%p     else

%p         A007954(n);

%p     end if:

%p end proc: # _R. J. Mathar_, Jan 11 2020

%t Table[If[n<11,0,Times@@IntegerDigits[n]],{n,0,100}] (* _Harvey P. Dale_, Aug 02 2016 *)

%o (PARI) a(n)=if(n<=9,0,n=digits(n); prod(i=1,#n,n[i])) \\ _Charles R Greathouse IV_, Aug 25 2014

%Y Cf. A007954.

%K nonn,base,easy

%O 0,13

%A _Felice Russo_, Oct 11 2010