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A274919 Sum of perimeters of the parts of the symmetric representation of sigma(n). 2
4, 8, 12, 16, 16, 24, 20, 32, 32, 40, 28, 48, 32, 52, 52, 64, 40, 72, 44, 80, 72, 76, 52, 96, 68, 88, 88, 112 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) is also the number of toothpicks added at n-th stage in the toothpick structure of the symmetric representation of sigma in two quadrants (without the axis x and y).

LINKS

Table of n, a(n) for n=1..28.

FORMULA

a(n) = 4*A244361(n) = 2*A244363(n) = A244371(n)/2.

EXAMPLE

Illustration of a(9) = 32:

.         12

.     _ _ _ _ _

.    |_ _ _ _ _|

.               _ _ 8

.              |_  |

.                |_|  _

.                    | |

.                    | |

.                    | |  12

.                    | |

.                    |_|

.

For n = 9 the symmetric representation of sigma(9) = 13 has three parts of areas 5, 3, 5 respectively. The perĂ­meters of the parts are 12, 8 and 12 as shown above. The sum of the perimeters is 12 + 8 + 12 = 32, so a(9) = 32.

CROSSREFS

Cf. A000203, A196020, A236104, A237270, A237271, A237593, A244361, A244363, A244370, A244371, A245092, A262626.

Sequence in context: A081747 A331061 A020647 * A196032 A130702 A053806

Adjacent sequences:  A274916 A274917 A274918 * A274920 A274921 A274922

KEYWORD

nonn,more

AUTHOR

Omar E. Pol, Dec 11 2016

STATUS

approved

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Last modified May 31 19:11 EDT 2020. Contains 334748 sequences. (Running on oeis4.)