A number (usually base 10 unless specified otherwise) which has no digitaddition generator. Such numbers were originally called Colombian numbers (S. 1974).
There are infinitely many such numbers, since an infinite sequence of self numbers
can be generated from the recurrence relation

(1)

for , 3, ..., where . The first few self numbers are 1, 3, 5, 7, 9, 20, 31,
42, 53, 64, 75, 86, 97, ... (OEIS A003052).

An infinite number of 2-self numbers (i.e., base-2 self numbers) can be generated by the sequence

(2)

for , 2, ..., where and is the number of digits in . An infinite number of -self numbers can be generated from the sequence

(3)

for , 3, ..., and

(4)

Joshi (1973) proved that if
is odd, then is a -self number iff is odd. Patel (1991) proved
that , , and are -self numbers in every even
base .

Cai, T. "On -Self Numbers and Universal Generated Numbers." Fib.
Quart.34, 144-146, 1996.Gardner, M. Time
Travel and Other Mathematical Bewilderments. New York: W. H. Freeman,
pp. 115-117, 122, 1988.Joshi, V. S. Ph.D. dissertation. Gujarat
University, Ahmadabad, 1973.Kaprekar, D. R. The Mathematics
of New Self-Numbers. Devaiali, pp. 19-20, 1963.Patel, R. B.
"Some Tests for -Self
Numbers." Math. Student56, 206-210, 1991.S., B. R.
"Solution to Problem E 2048." Amer. Math. Monthly81, 407,
1974.Sloane, N. J. A. Sequence A003052/M2404
in "The On-Line Encyclopedia of Integer Sequences."