A319839 Smallest fixed points (>0) of the base-2*n Kaprekar map.

9, 30, 105, 21, 495, 858, 65, 2040, 2907, 133, 5313, 6900, 225, 10962, 13485, 341, 19635, 23310, 481, 31980, 37023, 645, 48645, 55272, 833, 70278, 78705, 1045, 97527, 107970, 1281, 131040, 143715, 1541, 171465, 186588, 1825, 219450, 237237, 2133, 275643, 296310, 2465

Offset

1,1

Links

Seiichi Manyama, Table of n, a(n) for n = 1..100

Index entries for the Kaprekar map

Formula

a(n) = A319798(2*n).

Prog

(Ruby)
def f(k, n)
  ary = []
  while n > 0
    ary << n % k
    n /= k
  end
  ary
end
def g(k, ary)
  (0..ary.size - 1).inject(0){|s, i| s + ary[i] * k ** i}
end
def A319798(n)
  i = 1
  ary = [1]
  while g(n, ary) - g(n, ary.reverse) != i
    i += 1
    ary = f(n, i).sort
  end
  i
end
def A319839(n)
  (1..n).map{|i| A319798(2 * i)}
end
p A319839(20)

Crossrefs

Cf. A099009, A163205, A165016, A165055, A165094, A319798.

Sequence in context: A301988 A334853 A212517 * A274998 A000440 A300643

Adjacent sequences: A319836 A319837 A319838 * A319840 A319841 A319842

Keyword

nonn,base,look

Author

Seiichi Manyama, Sep 29 2018

Status

approved