A130753 A folded-back triangular sequence based on symmetry of CnH2*n+2 straight chain alkanes and the number of hydrogen atoms of a given symmetry type: Besides methane at 4 there are only three symmetry types: two CH3's->6: a single CH2->2, two CH2's->4.

4, 6, 6, 2, 6, 4, 6, 4, 2, 6, 4, 4, 6, 4, 4, 2, 6, 4, 4, 4, 6, 4, 4, 4, 2, 6, 4, 4, 4, 4, 6, 4, 4, 4, 4, 2, 6, 4, 4, 4, 4, 4, 6, 4, 4, 4, 4, 4, 2, 6, 4, 4, 4, 4, 4, 4, 6, 4, 4, 4, 4, 4, 4, 2, 6, 4, 4, 4, 4, 4, 4, 4, 6, 4, 4, 4, 4, 4, 4, 4, 2, 6, 4, 4, 4, 4, 4, 4, 4, 4, 6, 4, 4, 4, 4, 4, 4, 4, 4, 2, 6, 4, 4, 4, 4

Offset

1,1

Links

Table of n, a(n) for n=1..105.

Wikipedia, Alkane

Formula

a(n,m) = If[n == m == 1, 4, If[n == 1 && m >1, 6, If[Mod[m, 2] == 1 && n == Floor[m/2] + 1, 2, 4]]]

Example

{4},->Ch4
{6}, ->CH3CH3
{6, 2}, ->CH3CH2CH3
{6, 4}, ->CH3CH2CH2CH3
{6, 4, 2}, ->CH3CH2CH2CH2CH3
{6, 4, 4}, ->CH3CH2CH2CH2CH2CH3
{6, 4, 4, 2}, ->CH3CH2CH2CH2CH2CH2CH3
{6, 4, 4, 4}, ->CH3CH2CH2CH2CH2CH2CH2CH3

Mathematica

f[n_, m_] = If[n == m ==1, 4, If[n == 1 && m > 1, 6, If[Mod[m, 2] == 1 && n == Floor[m/2] + 1, 2, 4]]]; Table[Table[f[n, m], {n, 1, If[m == 1, 1, If[Mod[m, 2] == 0, Floor[m/2], Floor[m/2] + 1]]}], {m, 1, 20}]; Flatten[%]

Crossrefs

Sequence in context: A329217 A352592 A119858 * A021686 A019923 A019800

Adjacent sequences: A130750 A130751 A130752 * A130754 A130755 A130756

Keyword

nonn,tabf

Author

Roger L. Bagula, Jul 13 2007

Status

approved