A110947 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,5

LINKS

Table of n, a(n) for n=1..30.

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

PROG

(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

CROSSREFS

Odd-indexed terms are the same as A001044.

Sequence in context: A271086 A271292 A271094 * A372212 A270167 A270159

Adjacent sequences: A110944 A110945 A110946 * A110948 A110949 A110950

KEYWORD

nonn

AUTHOR

Simone Severini, Sep 25 2005

EXTENSIONS

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

STATUS

approved