A110947 a(n) = permanent of an n X n matrix M of zeros and ones defined as follows: if we concatenate the rows of M to form a vector v of length n^2, v_i = 1 only if i = 1 or a multiple of 2.

1, 1, 1, 0, 4, 0, 36, 0, 576, 0, 14400, 0, 518400, 0, 25401600, 0, 1625702400, 0, 131681894400, 0, 13168189440000, 0, 1593350922240000, 0, 229442532802560000, 0, 38775788043632640000, 0, 7600054456551997440000, 0

Offset: 1

Author

Simone Severini, Sep 25 2005

Keywords

• nonn

Crossrefs

Odd-indexed terms are the same as A001044.

Programs

PARI

a(n)={my(A=matrix(n,n,i,j,1-((i-1)*n+j)%2)); A[1,1]=1; matpermanent(A)} \\ Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007

PARI

a(n)=if(n==2,1,if(n%2,((n-1)/2)!^2)) \\ Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007

Formula

a(1)=a(2)=1 and for n>2: a(n)=0 if n=2*k, a(n)=k!^2 if n=2*k+1. - Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007

Extensions

Corrected and extended by Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007