A162213 a(n) = the smallest positive multiple of n with exactly n digits when written in binary.

1, 2, 6, 8, 20, 36, 70, 128, 261, 520, 1034, 2052, 4108, 8204, 16395, 32768, 65552, 131076, 262162, 524300, 1048593, 2097172, 4194326, 8388624, 16777225, 33554456, 67108878, 134217748, 268435484, 536870940, 1073741854, 2147483648

Offset: 1

Author

Leroy Quet, Jun 28 2009

Keywords

• base
• nonn
• easy

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A162214, A053041.

Programs

Maple

a := proc (n) local k: for k while nops(convert(k*n, base, 2)) <> n do end do; k*n end proc: seq(a(n), n = 1 .. 24); # Emeric Deutsch, Jul 10 2009
a:= n-> n*ceil(2^(n-1)/n): seq(a(n), n=1..40); # Alois P. Heinz, Jul 11 2009

Mathematica

Array[# Ceiling[2^(# - 1)/#] &, 32] (* Michael De Vlieger, Nov 04 2017 *)

Formula

a(n) = n * ceiling(2^(n-1)/n). - Alois P. Heinz, Jul 11 2009

Extensions

More terms from Emeric Deutsch and Alois P. Heinz, Jul 11 2009