OFFSET
1,1
COMMENTS
Self-describing numbers: between two digits "d" there are d digits.
a(n) has either 0 or 2 instances of any digit, hence even number of digits.
"Strong" means that every digit from 0 to the largest digit of a(n) must be present in a(n). See A108116 for the "weak" variant without this additional constraint.
Number of digits of a(n) == 0 or 2 (mod 8)
Largest element is a(2820) = 867315136875420024.
LINKS
D. Wilson, Complete table of n, a(n) for n = 1..2820
PROG
(Python)
def A132291gen(): # SL() is in A108116
for numd in range(1, 11):
dset = ("0123456789")[:numd]
s = [0 for _ in range(2*numd)]
for an in sorted(SL(dset, s)):
yield an
for n, an in enumerate(A132291gen(), start=1):
print(n, an) # Michael S. Branicky, Dec 14 2020
CROSSREFS
KEYWORD
base,easy,fini,full,nonn
AUTHOR
Eric Angelini, Jun 26 2005, Aug 10 2007
EXTENSIONS
Edited by N. J. A. Sloane, Nov 18 2007
STATUS
approved