A079806 Number of even numbers that can be formed by permuting the digits of n.

1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 1, 2, 1

Offset: 0

Author

Amarnath Murthy, Feb 06 2003

Keywords

• base
• easy
• nonn
• changed

Comments

Leading zeros are allowed. - Robert Israel, Aug 27 2025

Examples

			a(246) = 6 (the numbers are 246,264,426,462,624,642). a(384) = 4 (the numbers are 384,348,438,834).
		

Links

• Robert Israel, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A047726, A079807.

Programs

Maple

f:= proc(n) local L, T, m, x, i,j;
   L:= convert(n,base,10);
   for i from 0 to 9 do T[i]:= numboccur(i,L) od;
   m:= nops(L);
   x:= 0;
   for i in [0,2,4,6,8] do
     if T[i] > 0 then x:= x + (m-1)!/(T[i]-1)!/mul(T[j]!,j={0$9} minus {i}); fi;
   od;
   x
end proc;
map(f, [$0..100]); # Robert Israel, Aug 27 2025

Mathematica

Table[Count[FromDigits/@Permutations[IntegerDigits[n]],?EvenQ],{n,0,120}] (* _Harvey P. Dale, Jul 25 2020 *)

Extensions

More terms from Harvey P. Dale, Jul 25 2020