OFFSET
1,2
COMMENTS
The sequence is finite. Last term: 999999999888888887777777666666555554444333221.
Number of terms is 66712890763701234740813164553708284. - Zak Seidov, Jan 02 2007
Fixed points of A139337. - Reinhard Zumkeller, Apr 14 2008
Sequence contains squares (A181392) and cubes (A225886^3) but no higher powers, see Comments in A181392. - Giovanni Resta, May 19 2013
LINKS
T. D. Noe, Table of n, a(n) for n=1..21056 (terms < 10^10)
Michael S. Branicky, Python program
EXAMPLE
23323 is in the sequence because it has two 2's and three 3's.
23332 is in the sequence because it has two 2's and three 3's.
23333 is not in the sequence because it has only one 2 and four 3's.
PROG
(PARI) is(n)={ vecmin(n=vecsort(digits(n))) && #n==normlp(Set(n), 1) && !for(i=1, #n, n[i+n[i]-1]==n[i] || return; i+n[i]>#n || n[i+n[i]]>n[i] || return; n[i]>1 && i+=n[i]-1)} \\ M. F. Hasler, Sep 22 2014
(Python) # see link for a function that directly generates terms
def ok(n): s = str(n); return all(s.count(d) == int(d) for d in set(s))
def aupto(limit): return [m for m in range(1, limit+1) if ok(m)]
print(aupto(155555)) # Michael S. Branicky, Jan 22 2021
CROSSREFS
KEYWORD
base,easy,fini,nonn
AUTHOR
Eric Angelini, Jul 05 2005
STATUS
approved