This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A139669 Number of isomorphism classes of finite groups of order 11*2^n. 1
 1, 2, 4, 12, 42, 195, 1387, 19324, 1083472 (list; graph; refs; listen; history; text; internal format)
 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 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 A039301 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

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

Last modified October 16 13:26 EDT 2019. Contains 328089 sequences. (Running on oeis4.)