A032828 Numbers whose set of base-16 digits is {1,4}.

1, 4, 17, 20, 65, 68, 273, 276, 321, 324, 1041, 1044, 1089, 1092, 4369, 4372, 4417, 4420, 5137, 5140, 5185, 5188, 16657, 16660, 16705, 16708, 17425, 17428, 17473, 17476, 69905, 69908, 69953, 69956, 70673, 70676, 70721

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for 2-automatic sequences.

Formula

a(1)=1, a(2)=4; a(n) = 16*a(floor(n/2))+1 for n odd, otherwise a(n) = 16*a(floor((n-1)/2))+4. - Bruno Berselli, May 28 2012

Mathematica

FromDigits[#, 16]&/@Flatten[Table[Tuples[{1, 4}, n], {n, 5}], 1] (* Harvey P. Dale, Feb 02 2012 *)

Prog

(Magma) [n: n in [1..75000] | Set(IntegerToSequence(n, 16)) subset {1, 4}]; // Vincenzo Librandi, May 28 2012
(Maxima) a[1]:1$ a[2]:4$ a[n]:= if oddp(n) then 16*a[floor(n/2)]+1 else 16*a[floor((n-1)/2)]+4$ makelist(a[n], n, 1, 37); /* Bruno Berselli, May 28 2012 */
(Python)
def a(n): return int(bin(n+1)[3:].replace('1', '4').replace('0', '1'), 16)
print([a(n) for n in range(1, 38)]) # Michael S. Branicky, Aug 22 2021

Crossrefs

Sequence in context: A031033 A128981 A212748 * A193379 A022134 A041529

Adjacent sequences: A032825 A032826 A032827 * A032829 A032830 A032831

Keyword

nonn,base,easy

Author

Clark Kimberling

Status

approved