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A026739 Number of subgroups L of Z^n with the property that for every a in Z^n there exists precisely one b in L with d(a,b) <= 1. Here d denotes Euclidean distance. 0
1, 1, 2, 8, 72, 384, 3840, 80640, 645120, 10321920, 309657600, 3715891200, 102187008000, 3310859059200, 51011754393600, 1428329123020800, 68559797904998400, 1942527607308288000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..17.

FORMULA

a(n) = 2^n*n!*sum(1/|Aut(G)|), where the sum is over all isomorphism classes of Abelian groups of order 2*n+1.

CROSSREFS

Sequence in context: A062733 A180687 A296629 * A060635 A194499 A009478

Adjacent sequences:  A026736 A026737 A026738 * A026740 A026741 A026742

KEYWORD

easy,nonn

AUTHOR

Paul Boddington, Jan 26 2004

STATUS

approved

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Last modified April 25 16:08 EDT 2019. Contains 322461 sequences. (Running on oeis4.)