The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A007537 Number of proper covers of an n-set. (Formerly M5287) 7
 0, 1, 45, 15913, 1073579193, 4611686005542975085, 85070591730234615801280047645054636261, 28948022309329048855892746252171976961956366698726387156269151989162886489297 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Alois P. Heinz, Table of n, a(n) for n = 1..11 A. J. Macula, Covers of a finite set, Math. Mag., 67 (1994), 141-144. Eric Weisstein's World of Mathematics, Proper Cover. FORMULA a(n) ~ 2^(2^n)/4. - Vaclav Kotesovec, Jul 02 2016 MAPLE A007537 := proc(n) 1/2*sum((-1)^k*binomial(n, k)*2^(2^(n-k)), k=0..n)-2^(2^n)/4 end; MATHEMATICA Table[1/2 Sum[(-1)^k Binomial[n, k]2^(2^(n-k)), {k, 0, n}]-2^2^n/4, {n, 8}] (* Harvey P. Dale, Oct 31 2011 *) CROSSREFS Cf. A003465. Sequence in context: A201004 A171118 A199521 * A287434 A225991 A125113 Adjacent sequences:  A007534 A007535 A007536 * A007538 A007539 A007540 KEYWORD nonn,easy,nice AUTHOR EXTENSIONS One more term from Emeric Deutsch, Aug 01 2005 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 April 13 07:51 EDT 2021. Contains 342935 sequences. (Running on oeis4.)