A317947 Concatenate n and n-1 in binary.

10, 101, 1110, 10011, 101100, 110101, 111110, 1000111, 10011000, 10101001, 10111010, 11001011, 11011100, 11101101, 11111110, 100001111, 1000110000, 1001010001, 1001110010, 1010010011, 1010110100, 1011010101, 1011110110, 1100010111, 1100111000, 1101011001, 1101111010, 1110011011, 1110111100

Offset: 1

Author

N. J. A. Sloane, Aug 11 2018

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000523, A007088, A127423 (base 10 version).

Programs

Maple

f:= proc(n) local A;
  A:= convert(n-1,binary);
  10^length(A)*convert(n,binary)+A
end proc:
f(1):= 10:
map(f, [$1..100]); # Robert Israel, Aug 12 2018

PARI

zbinary(n) = if (n, binary(n), [0]);
a(n) = fromdigits(concat(zbinary(n), zbinary(n-1))); \\ Michel Marcus, Aug 12 2018

Formula

a(n) = A007088(n-1)+10^(1+A000523(n-1))*A007088(n) for n >= 2. - Robert Israel, Aug 12 2018

Extensions

More terms from Robert Israel, Aug 12 2018