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

0,21

Comments

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

Links

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

Example

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

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 *)

Crossrefs

Cf. A047726, A079807.

Sequence in context: A133162 A276172 A322028 * A342845 A045887 A056832

Adjacent sequences: A079803 A079804 A079805 * A079807 A079808 A079809

Keyword

base,easy,nonn

Author

Amarnath Murthy, Feb 06 2003

Extensions

More terms from Harvey P. Dale, Jul 25 2020

Status

approved