A284068 Numbers whose smallest decimal digit is 7.

7, 77, 78, 79, 87, 97, 777, 778, 779, 787, 788, 789, 797, 798, 799, 877, 878, 879, 887, 897, 977, 978, 979, 987, 997, 7777, 7778, 7779, 7787, 7788, 7789, 7797, 7798, 7799, 7877, 7878, 7879, 7887, 7888, 7889, 7897, 7898, 7899, 7977, 7978, 7979, 7987, 7988, 7989

Offset: 1

Author

Jaroslav Krizek, Mar 23 2017

Keywords

• nonn
• base

Comments

Numbers n such that A054054(n) = 7.

Prime terms are in A106107.

Crossrefs

Cf. Sequences of numbers whose smallest decimal digit is k (for k = 0..9): A011540 (k = 0), A284062 (k = 1), A284063 (k = 2), A284064 (k = 3), A284065 (k = 4), A284066 (k = 5), A284067 (k = 6), this sequence (k = 7), A284069 (k = 8), A002283 (k = 9).

Programs

Magma

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

Mathematica

Select[Range[8000], Min[IntegerDigits[#]] == 7 &] (* Giovanni Resta, Mar 23 2017 *)

PARI

isok(n) = vecmin(digits(n)) == 7; \\ Michel Marcus, Mar 25 2017