A366964 Numbers whose difference between the largest and smallest digits is equal to 7.

18, 29, 70, 81, 92, 107, 118, 128, 138, 148, 158, 168, 170, 178, 181, 182, 183, 184, 185, 186, 187, 188, 207, 218, 229, 239, 249, 259, 269, 270, 279, 281, 289, 292, 293, 294, 295, 296, 297, 298, 299, 307, 318, 329, 370, 381, 392, 407, 418, 429, 470, 481, 492

Offset: 1

Author

Stefano Spezia, Oct 30 2023

Keywords

• nonn
• base
• easy

Comments

The number of n-digit terms is 23*8^(n-1) - 41*7^(n-1) + 2^n*3^(n+1).

Crossrefs

Cf. A037904.

Cf. A010785 (difference = 0), A366958 (difference = 1), A366959 (difference = 2), A366960 (difference = 3), A366961 (difference = 4), A366962 (difference = 5), A366963 (difference = 6), A366965 (difference = 8), A366966 (difference = 9).

Programs

Mathematica

Select[Range[500],Max[d=IntegerDigits[#]]-Min[d]==7 &]

PARI

isok(n) = my(d=digits(n)); vecmax(d) - vecmin(d) == 7; \\ Michel Marcus, Nov 05 2023

Python

def ok(n): return max(d:=list(map(int, str(n))))-min(d) == 7
print([k for k in range(500) if ok(k)]) # Michael S. Branicky, Oct 30 2023