A363121 Primitive terms of A116882: terms k of A116882 such that k/2 is not a term of A116882.

1, 12, 40, 56, 144, 176, 208, 240, 544, 608, 672, 736, 800, 864, 928, 992, 2112, 2240, 2368, 2496, 2624, 2752, 2880, 3008, 3136, 3264, 3392, 3520, 3648, 3776, 3904, 4032, 8320, 8576, 8832, 9088, 9344, 9600, 9856, 10112, 10368, 10624, 10880, 11136, 11392, 11648, 11904

Offset

1,2

Comments

If k is a term of this sequence then k*2^m is a term of A116882 for any m >= 0.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = (2*n-1)*2^A070941(n-1), for n > 1.

Mathematica

q[n_] := 2^(2*IntegerExponent[n, 2]) >= n; Join[{1}, Select[Range[2, 12000, 2], q[#] && !q[#/2] &]]
(* Alternative: *)
a[1] = 1; a[n_] := (2*n - 1)*2^IntegerLength[2*n - 1, 2]; Array[a, 100]

Prog

(PARI) a(n) = if(n == 1, 1, (2*n - 1)*2^length(binary(2*n - 1)));
(Python)
def A363121(n): return (m:=2*n-1)<<m.bit_length() if n>1 else 1 # Chai Wah Wu, May 17 2023

Crossrefs

Cf. A070941, A116882.

Sequence in context: A292544 A345924 A114815 * A353839 A383015 A175583

Adjacent sequences: A363118 A363119 A363120 * A363122 A363123 A363124

Keyword

nonn,easy,changed

Author

Amiram Eldar, May 16 2023

Status

approved