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Numbers n with digits 5 and 9 only.
4

%I #12 Sep 08 2022 08:46:19

%S 5,9,55,59,95,99,555,559,595,599,955,959,995,999,5555,5559,5595,5599,

%T 5955,5959,5995,5999,9555,9559,9595,9599,9955,9959,9995,9999,55555,

%U 55559,55595,55599,55955,55959,55995,55999,59555,59559,59595,59599,59955,59959

%N Numbers n with digits 5 and 9 only.

%C Prime terms are in A020468.

%H Michael S. Branicky, <a href="/A284382/b284382.txt">Table of n, a(n) for n = 1..10000</a>

%t Join @@ ((FromDigits /@ Tuples[{5, 9}, #]) & /@ Range@ 5) (* _Giovanni Resta_, Mar 28 2017 *)

%o (Magma) [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {5, 9}]

%o (Python)

%o def a(n): return int(bin(n+1)[3:].replace('0', '5').replace('1', '9'))

%o print([a(n) for n in range(1, 45)]) # _Michael S. Branicky_, May 09 2021

%Y Numbers n with digits 5 and k only for k = 0 - 4 and 6 - 9: A169964 (k = 0), A276037 (k = 1), A072961 (k = 2), A284379 (k = 3), A256290 (k = 4), A256291 (k = 6), A284380 (k = 7), A284381 (k = 8), this sequence (k = 9).

%K nonn,base

%O 1,1

%A _Jaroslav Krizek_, Mar 28 2017