A029746 Numbers of the form 2^k or 7*2^k.

1, 2, 4, 7, 8, 14, 16, 28, 32, 56, 64, 112, 128, 224, 256, 448, 512, 896, 1024, 1792, 2048, 3584, 4096, 7168, 8192, 14336, 16384, 28672, 32768, 57344, 65536, 114688, 131072, 229376, 262144, 458752, 524288, 917504, 1048576, 1835008, 2097152

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (0,2).

Crossrefs

Cf. A000079, A005009, A029744, A029748.

Programs

Mathematica

Sort[Flatten[{#,7#}&/@(2^Range[0,21])]] (* or *) CoefficientList[Series[ (1+2x+2x^2+3x^3)/(1-2x^2),{x,0,50}],x]  (* Harvey P. Dale, Apr 23 2011 *)

PARI

a(n)=if(n<0,0,if(n<2,2^n,if(n%2,7/2,2)*2^(n\2)))

Formula

G.f.: (1+2x+2x^2+3x^3)/(1-2x^2). - Michael Somos, Nov 05 2002

Sum_{n>=0} 1/a(n) = 16/7. - Amiram Eldar, Jan 17 2022