The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A241223 Number of triangles on a centered hexagonal grid of size n. 7
 0, 32, 900, 7380, 34676, 118044, 325872, 775856, 1653888, 3237984, 5923028, 10249596, 16938588, 26924036, 41393424, 61830480, 90059672, 128293728, 179185500, 245889068, 332107188, 442162836, 581060024, 754545360, 969196896, 1232477192, 1552824900 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A centered hexagonal grid of size n is a grid with A003215(n-1) points forming a hexagonal lattice. LINKS Andrew Howroyd, Table of n, a(n) for n = 1..200 Eric Weisstein's World of Mathematics, Hex Number. Eric Weisstein's World of Mathematics, Triangle. FORMULA a(n) = A240826(n) - A241222(n). a(n) = A241224(n) + A241225(n) + A241226(n) = A241227(n) + A241228(n). EXAMPLE For n = 2 the 32 triangles are the following: /. *     * *     * .     . .     . .     . .     . *     * * . * *   . * .   * * .   * * .   . * .   . * *   * . *   . . . \. .     . .     . .     * .     * *     . *     . .     * . - /* .     . .     . *     * .     . *     * *     * .     . * * . .   * . *   . . .   . . *   . . *   . . .   * . *   * . . \. *     * .     * *     . *     * .     . *     . .     * . - /* .     . .     * *     * *     * .     . .     . .     . * . . .   * . *   . . *   * . .   * . .   * . .   . . *   . . * \* *     . *     . .     . .     * .     * *     * *     . * - /* .     . *     * .     . .     . .     . *     * .     . * . * *   * * .   . * .   * * .   . * *   . * .   . . *   * . . \. .     . .     * .     . *     * .     . *     * .     . * CROSSREFS Cf. A045996. Sequence in context: A222606 A283854 A160314 * A283412 A227441 A067820 Adjacent sequences:  A241220 A241221 A241222 * A241224 A241225 A241226 KEYWORD nonn AUTHOR Martin Renner, Apr 17 2014 EXTENSIONS a(7) from Martin Renner, May 31 2014 a(8)-a(22) from Giovanni Resta, May 31 2014 Terms a(23) and beyond from Andrew Howroyd, Sep 18 2017 STATUS approved

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

Last modified August 9 17:13 EDT 2022. Contains 356026 sequences. (Running on oeis4.)