A213255 2^(n-1) - floor((2^(n-1) - 1)/(n-1)).

1, 3, 6, 13, 26, 54, 110, 225, 456, 922, 1862, 3755, 7562, 15214, 30584, 61441, 123362, 247581, 496694, 996148, 1997288, 4003654, 8023886, 16078166, 32212255, 64527754, 129246702, 258848476, 518358122, 1037950430, 2078209982, 4160749569, 8329633544

Offset

2,2

Comments

Lower bounds of the decycling numbers of n-cubes for n >= 9.

Links

Arkadiusz Wesolowski, Table of n, a(n) for n = 2..800

Sheng Bau, The Decycling Number of Graphs

Formula

a(n) = 2^(n-1) - floor((2^(n-1) - 1)/(n-1)).

a(n) = ceiling(2^(n-1) - (2^(n-1) - 1)/(n-1)).

Example

a(8) = 110 because 2^7 - (2^7 - 1)/7 = 109.8571428571....

Mathematica

Table[Ceiling[2^(n - 1) - (2^(n - 1) - 1)/(n - 1)], {n, 2, 34}]

Prog

(Magma) [Ceiling(2^(n-1)-(2^(n-1)-1)/(n-1)) : n in [2..34]];
(PARI) for(n=2, 34, print1(ceil(2^(n-1)-(2^(n-1)-1)/(n-1)), ", "))

Crossrefs

Cf. A005009.

Sequence in context: A267581 A320733 A164991 * A215985 A215986 A215987

Adjacent sequences: A213252 A213253 A213254 * A213256 A213257 A213258

Keyword

easy,nonn

Author

Arkadiusz Wesolowski, Jun 07 2012

Status

approved