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A171757
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Even numbers whose binary expansion begins 10.
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9
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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
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1024 from R. J. Mathar)
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FORMULA
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a(n) = 2*A004761(n+1). - Jon Maiga / Georg Fischer, Jun 24 2021
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MAPLE
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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
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MATHEMATICA
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Select[Range[2, 200, 2], IntegerDigits[#, 2][[1 ;; 2]] == {1, 0} &] (* Amiram Eldar, Sep 01 2020 *)
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PROG
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(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
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CROSSREFS
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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
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KEYWORD
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nonn,base
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AUTHOR
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N. J. A. Sloane, Oct 12 2010
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STATUS
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approved
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