A169964 Numbers whose decimal expansion contains only 0's and 5's.

0, 5, 50, 55, 500, 505, 550, 555, 5000, 5005, 5050, 5055, 5500, 5505, 5550, 5555, 50000, 50005, 50050, 50055, 50500, 50505, 50550, 50555, 55000, 55005, 55050, 55055, 55500, 55505, 55550, 55555, 500000, 500005, 500050, 500055, 500500, 500505, 500550, 500555

Offset: 1

Author

N. J. A. Sloane, Aug 07 2010

Keywords

• nonn
• base
• easy

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to carryless arithmetic

Crossrefs

Cf. A007088, A014263, A169965, A169966, A169967.

Cf. A078244, A204093, A204094, A204095, A097256.

Programs

Haskell

a169964 n = a169964_list !! (n-1)
a169964_list = map (* 5) a007088_list
-- Reinhard Zumkeller, Jan 10 2012

Mathematica

Map[FromDigits,Tuples[{0,5},6]] (* Paolo Xausa, Oct 30 2023 *)

PARI

print1(0);for(d=1,5,for(n=2^(d-1),2^d-1,print1(", ");forstep(i=d-1,0,-1,print1((n>>i)%2*5)))) \\ Charles R Greathouse IV, Nov 16 2011

Formula

a(n+1) = Sum_{k>=0} A030308(n,k)*A093143(k+1). - Philippe Deléham, Oct 16 2011

a(n) = 5 * A007088(n-1).