A128244 - OEIS

%I #13 Dec 09 2016 03:50:14

%S 1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,0,2,3,4,5,6,7,8,9,0,1,3,4,5,6,7,

%T 8,9,0,1,2,4,5,6,7,8,9,0,1,2,3,5,6,7,8,9,0,1,2,3,4,6,7,8,9,0,1,2,3,4,

%U 5,7,8,9,0,1,2,3,4,5,6,8,9,0,1,2,3,4,5,6,7,9,0,1,2,3,4,5,6,7,8,1,2,3,4,5,6

%N Let s be the sum of the digits of n; a(n) is the product of the digits of s.

%C The sequence is equal to A053837 up to the 488th term.

%H Robert Israel, <a href="/A128244/b128244.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A007954(A007953(n)). - _Michel Marcus_, Dec 09 2016

%e a(345)=2 because 3+4+5=12 and 1*2=2.

%p P:=proc(n) local i,k,w; for i from 1 by 1 to n do w:=0; k:=i; while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; k:=w; w:=1; while k>0 do w:=w*(k-(trunc(k/10)*10)); k:=trunc(k/10); od; print(w); od; end: P(500);

%p # alternative

%p f:= n -> convert(convert(convert(convert(n,base,10),`+`),base,10),`*`):

%p map(f, [$1..100]); # _Robert Israel_, Dec 09 2016

%t sdpd[n_]:=Module[{s=Total[IntegerDigits[n]]},Times@@IntegerDigits[s]]; Array[sdpd, 110] (* _Harvey P. Dale_, Dec 17 2013 *)

%Y Cf. A053837, A007953, A007954.

%K easy,nonn,base

%O 1,2

%A _Paolo P. Lava_ and _Giorgio Balzarotti_, May 03 2007

%E Offset corrected by _Robert Israel_, Dec 09 2016