A066309 - OEIS

%I #20 Dec 04 2024 23:05:12

%S 10,11,12,13,20,21,22,30,31,32,40,41,50,51,60,61,70,71,80,81,90,91,

%T 100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,

%U 117,118,119,120,121,122,123,124,125,126,130,131,132,133,134,140,141,142

%N Numbers k such that k > (product of digits of k) * (sum of digits of k).

%H Harry J. Smith, <a href="/A066309/b066309.txt">Table of n, a(n) for n = 1..1000</a>

%e 13 is in the sequence because (1*3)*(1+3) = 3*4 = 12 < 13.

%e 125 is a term because (1*2*5)*(1+2+5) = 10*8 = 80 < 125.

%t asum[x_] := Apply[Plus, IntegerDigits[x]] apro[x_] := Apply[Times, IntegerDigits[x]] sz[x_] := asu[x]*apro[x] Do[s=sz[n]; If[Greater[n, s], Print[n]], {n, 1, 1000}]

%t okQ[n_]:=Module[{idn=IntegerDigits[n]},n> Total[idn]Times@@idn];Select[Range[150],okQ]  (* _Harvey P. Dale_, Mar 12 2011 *)

%o (ARIBAS): function a066312(a,b: integer); var n,k,j,p,d: integer; s: string; begin for n := a to b do s := itoa(n); k := 0; p := 1; for j := 0 to length(s) - 1 do d := atoi(s[j..j]); k := k + d; p := p*d; end; if n > p*k then write(n,","); end; end; end; a066312(0,150).

%o (PARI) isok(k) = {my(d=digits(k)); k > vecprod(d) * vecsum(d)} \\ _Harry J. Smith_, Feb 10 2010

%Y Cf. A038369, A049101-A049106, A034710, A061672, A066306, A066307.

%K base,nonn

%O 1,1

%A _Labos Elemer_ and _Klaus Brockhaus_, Dec 13 2001