login
A132291
Base 10 strong Skolem-Langford numbers.
7
12132003, 23121300, 30023121, 31213200, 1214230043, 1312432004, 2342131400, 2412134003, 3004312142, 3400324121, 4002342131, 4131243200, 1213267345006475, 1213275364005746, 1214267540036573, 1214273645300765, 1214275640035763, 1215247365430076
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.
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
Base 10 Skolem-Langford numbers are in A108116.
Base 10 weaker Skolem-Langford numbers are in A357826.
Sequence in context: A022227 A206750 A178056 * A263391 A204888 A268418
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