[seqfan] A004720

[Sean A. Irvine]

Something is wrong with A004720.  To be consistent with A004721 through
A004728, numbers that leave no digits after deleting 1s should simply be
omitted. But instead A004720 appears to put in 0 for such numbers, e.g. for
11 and 111, which is really what A004176 is (cf. also A004177 etc. for
other digits).

Alternatively if the current way is accepted, then there should be another
0 at the beginning since the sequence is supposed to be for nonnegative
integers, and we would have both 0 and 1 being represented by 1.  But then
A004720 would be exactly like A004176.

My opinion is that A004720 should be consistent with A004721 through
A004728 and the extra zeros simply deleted, but that would invalidate the
bfile and probably the existing programs.

Sean.