A240135 a(n) = composite(n)*2^(n - 3).

1, 3, 8, 18, 40, 96, 224, 480, 1024, 2304, 5120, 10752, 22528, 49152, 102400, 212992, 442368, 917504, 1966080, 4194304, 8650752, 17825792, 36700160, 75497472, 159383552, 327155712, 671088640, 1409286144, 2952790016, 6039797760, 12348030976, 25769803776, 52613349376

Offset

1,2

Links

Table of n, a(n) for n=1..33.

Formula

a(n) = A000079(n) * A002808(n) / 8.

Example

a(1) = 1 because composite(1) * 2^(1-3) = 4 * 2^(-2) = 1;
a(2) = 3 because composite(2) * 2^(2-3) = 6 * 2^(-1) = 3;
a(3) = 8 because composite(3) * 2^(3-3) = 8 * 2^0 = 8.

Mathematica

#[[1]]*2^(#[[2]]-3)&/@Module[{cs=Select[Range[50], CompositeQ]}, Thread[ {cs, Range[Length[cs]]}]] (* Harvey P. Dale, Oct 08 2018 *)

Prog

(PARI) my(k=1); forcomposite(n=1, 49, print1(n<<(k-3)", "); k++) \\ Bruce Nye, May 07 2026

Crossrefs

Cf. A000079, A002808.

Sequence in context: A294591 A080692 A117080 * A066425 A395405 A026679

Adjacent sequences: A240132 A240133 A240134 * A240136 A240137 A240138

Keyword

nonn,less

Author

Gerasimov Sergey, Apr 02 2014

Extensions

a(33) from Bruce Nye, May 07 2026

Status

approved