A283610 Numbers n whose largest decimal digit is 7.

7, 17, 27, 37, 47, 57, 67, 70, 71, 72, 73, 74, 75, 76, 77, 107, 117, 127, 137, 147, 157, 167, 170, 171, 172, 173, 174, 175, 176, 177, 207, 217, 227, 237, 247, 257, 267, 270, 271, 272, 273, 274, 275, 276, 277, 307, 317, 327, 337, 347, 357, 367, 370, 371, 372

Offset: 1

Author

Jaroslav Krizek, Mar 19 2017

Keywords

• nonn
• base
• easy

Comments

Numbers n such that A054055(n) = 7.

Number of terms less than 10^n is 8^n - 7^n.

Prime terms are in A106095.

Links

• Muniru A Asiru, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A054055, A106095.

Cf. Sequences of numbers n whose largest decimal digit is k (for k = 1 - 9): A007088 (k = 1), A277964 (k = 2), A277965 (k = 3), A277966 (k = 4), A283608 (k = 5), A283609 (k = 6), this sequence (k = 7), A283611 (k = 8), A011539 (k = 9).

Programs

GAP

Filtered([1..380],n->Maximum(ListOfDigits(n))=7); # Muniru A Asiru, Feb 27 2019

Magma

[n: n in [1..100000] | Maximum(Setseq(Set(Sort(&cat[Intseq(n)])))) eq 7]

Mathematica

Select[Range[1000], Max[IntegerDigits[#]] == 7 &] (* Giovanni Resta, Mar 19 2017 *)

PARI

for(n=1, 500, if(vecmax(digits(n))==7, print1(n,", "))) \\ Indranil Ghosh, Mar 19 2017

Python

from sympy.ntheory.factor_ import digits
[n for n in range(1, 401) if max(digits(n)[1:]) == 7]  # Indranil Ghosh, Mar 19 2017