login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A130840 a(n) = floor((1/16)*(16 + 2^n - 8*n + 8*n^2)). 1
1, 1, 2, 4, 8, 13, 20, 30, 45, 69, 110, 184, 323, 591, 1116, 2154, 4217, 8329, 16538, 32940, 65727, 131283, 262376, 524542, 1048853, 2097453, 4194630, 8388960, 16777595, 33554839, 67109300 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

A face number function for a type of exceptional group expansion using Euler's formula V=E-F+2.

Derived in Mathematica to give known exceptional group polyhedron sequence: (Platonic solids) e = n*(n - 1); v = f - 2^(n - 3); Solve[v + f - e - 2 == 0, f] Table[Round[{-e, v, f}], {n, 1, 7}] {{0, 1, 1}, {-2, 2, 2}, {-6, 4, 4}, {-12, 6, 8}, {-20, 9, 13}, {-30, 12, 20}, {-42, 14, 30}} Table[Apply[Plus, Round[{-e, v, f}]], {n, 1, 7}]->{2, 2, 2, 2, 2, 2, 2} This result is just a sequence of numbers that seem to work.

LINKS

Table of n, a(n) for n=1..31.

MATHEMATICA

Table[Round[(1/16)(16 + 2^n - 8 n + 8 n^2)], {n, 0, 30}]

CROSSREFS

Sequence in context: A173721 A247587 A061866 * A115266 A026039 A004978

Adjacent sequences:  A130837 A130838 A130839 * A130841 A130842 A130843

KEYWORD

nonn

AUTHOR

Roger L. Bagula, Jul 19 2007

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified December 21 18:17 EST 2014. Contains 252324 sequences.