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A366958
Numbers whose difference between the largest and smallest digits is equal to 1.
8
10, 12, 21, 23, 32, 34, 43, 45, 54, 56, 65, 67, 76, 78, 87, 89, 98, 100, 101, 110, 112, 121, 122, 211, 212, 221, 223, 232, 233, 322, 323, 332, 334, 343, 344, 433, 434, 443, 445, 454, 455, 544, 545, 554, 556, 565, 566, 655, 656, 665, 667, 676, 677, 766, 767, 776, 778, 787, 788
OFFSET
1,1
COMMENTS
The number of n-digit terms of this sequence is 17*A000225(n-1).
MATHEMATICA
Select[Range[800], Max[d=IntegerDigits[#]]-Min[d]==1 &]
PROG
(PARI) isok(n) = my(d=digits(n)); vecmax(d) - vecmin(d) == 1; \\ Michel Marcus, Oct 30 2023
(Python)
def ok(n): return max(d:=list(map(int, str(n))))-min(d) == 1
print([k for k in range(800) if ok(k)]) # Michael S. Branicky, Oct 30 2023
(Python) # faster version for large terms
from itertools import count, islice, product
def agen(diff=1): # generator of terms; change diff for A366960-A366966
for digits in count(2):
s = set()
for lo in range(10-diff):
hi = lo + diff
allowed = list(range(lo, hi+1))
for p in product(allowed, repeat=digits):
if p[0]==0 or lo not in p or hi not in p: continue
s.add(int("".join(map(str, p))))
yield from sorted(s)
print(list(islice(agen(), 60))) # Michael S. Branicky, Oct 30 2023
CROSSREFS
Cf. A010785 (difference = 0), A366959 (difference = 2), A366960 (difference = 3), A366961 (difference = 4), A366962 (difference = 5), A366963 (difference = 6), A366964 (difference = 7), A366965 (difference = 8), A366966 (difference = 9).
Sequence in context: A320170 A082927 A108965 * A341002 A175885 A061870
KEYWORD
nonn,base,easy
AUTHOR
Stefano Spezia, Oct 30 2023
STATUS
approved