

A139669


Number of isomorphism classes of finite groups of order 11*2^n.


1




OFFSET

0,2


COMMENTS

This appears to be the smallest possible number of groups of order q*2^n for an odd number q.
Apparently, a(n) is also the number of isomorphism classes of finite groups of order 19*2^n and, more generally, of order p*2^n for primes p such that p is congruent to 3 modulo 4 and p+1 is not a power of 2.


REFERENCES

J. H. Conway et al., The Symmetries of Things, Peters, 2008, p. 206.


LINKS

Table of n, a(n) for n=0..8.
John H. Conway, Heiko Dietrich and E. A. O'Brien, Counting groups: gnus, moas and other exotica.


FORMULA

a(n) = A000001(11*2^n).  Max Alekseyev, Apr 26 2010


EXAMPLE

a(2) is the number of groups of order 11*2^2=44, which is 4 and also the number of groups of order 19*2^2=76, 23*2^2=92, etc.


MAPLE

A139669 := n > GroupTheory[NumGroups](11*2^n);


CROSSREFS

Sequence in context: A200222 A063179 A096802 * A179973 A275780 A334272
Adjacent sequences: A139666 A139667 A139668 * A139670 A139671 A139672


KEYWORD

hard,more,nonn


AUTHOR

Anthony D. Elmendorf (aelmendo(AT)calumet.purdue.edu), Jun 12 2008


EXTENSIONS

a(8) from Max Alekseyev, Dec 24 2014


STATUS

approved



