cp's OEIS Frontend

A366958 Numbers whose difference between the largest and smallest digits is equal to 1.

%I A366958 #25 Nov 06 2023 11:07:58
%S A366958 10,12,21,23,32,34,43,45,54,56,65,67,76,78,87,89,98,100,101,110,112,
%T A366958 121,122,211,212,221,223,232,233,322,323,332,334,343,344,433,434,443,
%U A366958 445,454,455,544,545,554,556,565,566,655,656,665,667,676,677,766,767,776,778,787,788
%N A366958 Numbers whose difference between the largest and smallest digits is equal to 1.
%C A366958 The number of n-digit terms of this sequence is 17*A000225(n-1).
%t A366958 Select[Range[800],Max[d=IntegerDigits[#]]-Min[d]==1 &]
%o A366958 (PARI) isok(n) = my(d=digits(n)); vecmax(d) - vecmin(d) == 1; \\ _Michel Marcus_, Oct 30 2023
%o A366958 (Python)
%o A366958 def ok(n): return max(d:=list(map(int, str(n))))-min(d) == 1
%o A366958 print([k for k in range(800) if ok(k)]) # _Michael S. Branicky_, Oct 30 2023
%o A366958 (Python) # faster version for large terms
%o A366958 from itertools import count, islice, product
%o A366958 def agen(diff=1): # generator of terms; change diff for A366960-A366966
%o A366958     for digits in count(2):
%o A366958         s = set()
%o A366958         for lo in range(10-diff):
%o A366958             hi = lo + diff
%o A366958             allowed = list(range(lo, hi+1))
%o A366958             for p in product(allowed, repeat=digits):
%o A366958                 if p[0]==0 or lo not in p or hi not in p: continue
%o A366958                 s.add(int("".join(map(str, p))))
%o A366958         yield from sorted(s)
%o A366958 print(list(islice(agen(), 60))) # _Michael S. Branicky_, Oct 30 2023
%Y A366958 Cf. A000225, A037904.
%Y A366958 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).
%K A366958 nonn,base,easy
%O A366958 1,1
%A A366958 _Stefano Spezia_, Oct 30 2023