A171757 Even numbers whose binary expansion begins 10.

2, 4, 8, 10, 16, 18, 20, 22, 32, 34, 36, 38, 40, 42, 44, 46, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 166, 168, 170, 172, 174, 176, 178

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1024 from R. J. Mathar)

Formula

a(n) = 2*A004761(n+1). - Jon Maiga / Georg Fischer, Jun 24 2021

Maple

n := 1 ;
for k from 2 to 4000 by 2 do
    dgs := convert(k, base, 2) ;
    if op(-1, dgs) = 1 and op(-2, dgs) = 0 then
        printf("%d %d\n", n, k) ;
        n := n+1 ;
    end if;
end do: # R. J. Mathar, Jan 31 2015

Mathematica

Select[Range[2, 200, 2], IntegerDigits[#, 2][[1 ;; 2]] == {1, 0} &] (* Amiram Eldar, Sep 01 2020 *)

Prog

(Python)
from itertools import count, product, takewhile
def agen(): # generator for sequence
    yield 2
    for digits in count(0):
        for mid in product("01", repeat=digits):
            yield int("10" + "".join(mid) + "0", 2)
def aupto(lim): return list(takewhile(lambda x: x <= lim, agen()))
print(aupto(180)) # Michael S. Branicky, Jun 24 2021
(PARI) isok(m) = if (!(m%2), my(b=binary(m)); (b[1]==1) && (b[2]==0)); \\ Michel Marcus, Jun 24 2021

Crossrefs

Cf. A004761, A171758, A171763, A171764.

A subsequence of A004754.

Sequence in context: A076919 A336659 A341655 * A350780 A128106 A354776

Adjacent sequences: A171754 A171755 A171756 * A171758 A171759 A171760

Keyword

nonn,base

Author

N. J. A. Sloane, Oct 12 2010

Status

approved