A319724 Write n in 7-ary, sort digits into decreasing order.

0, 1, 2, 3, 4, 5, 6, 7, 8, 15, 22, 29, 36, 43, 14, 15, 16, 23, 30, 37, 44, 21, 22, 23, 24, 31, 38, 45, 28, 29, 30, 31, 32, 39, 46, 35, 36, 37, 38, 39, 40, 47, 42, 43, 44, 45, 46, 47, 48, 49, 56, 105, 154, 203, 252, 301, 56, 57, 106, 155, 204, 253, 302, 105, 106, 113, 162

Offset: 0

Author

Seiichi Manyama, Sep 26 2018

Keywords

• nonn
• base
• look
• easy

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..2400

Crossrefs

b-ary: A073138 (b=2), A319651 (b=3), A319720 (b=4), A319722 (b=5), A319723 (b=6), this sequence (b=7), A319725 (b=8), A319726 (b=9), A004186 (b=10).

Cf. A165071, A319655.

Programs

Mathematica

Table[FromDigits[ReverseSort[IntegerDigits[n, 7]], 7], {n, 0, 100}] (* Paolo Xausa, Aug 07 2024 *)

PARI

a(n) = fromdigits(vecsort(digits(n, 7), , 4), 7); \\ Michel Marcus, Sep 26 2018

Ruby

def A(k, n)
  (0..n).map{|i| i.to_s(k).split('').sort.reverse.join.to_i(k)}
end
p A(7, 100)

Formula

n <= a(n) < 7n. - Charles R Greathouse IV, Aug 07 2024