|
Search: id:A073364
|
|
|
| A073364 |
|
Number of permutations p of (1,2,3,...,n) such that k+p(k) is prime for 1<=k<=n. |
|
+0
6
|
|
| 1, 1, 1, 4, 1, 9, 4, 36, 36, 676, 400, 9216, 3600, 44100, 36100, 1223236, 583696, 14130081, 5461569, 158180929, 96275344, 5486661184, 2454013444, 179677645456, 108938283364, 5446753133584, 4551557699844, 280114147765321
(list; graph; listen)
|
|
|
OFFSET
|
1,4
|
|
|
COMMENT
|
a(n)=permanent(m), where the n X n matrix m is defined by m(i,j) = 1 or 0, depending on whether i+j is prime or composite respectively. - T. D. Noe (noe(AT)sspectra.com), Oct 16 2007
|
|
FORMULA
|
a(2n)=A000341(n)^2 and a(2n+1)=A134293(n)^2. - T. D. Noe (noe(AT)sspectra.com), Oct 16 2007
|
|
PROGRAM
|
(PARI) a(n)=sum(k=1, n!, if(sum(i=1, n, isprime(i+component(numtoperm(n, k), i)))-n, 0, 1))
(PARI) a(n) = c=0; for(k=1, n!, for(i=1, n, if(isprime(i+numtoperm(n, k)[i]), if(i==n, c++), break))); c (from Rick Shepherd)
|
|
CROSSREFS
|
Sequence in context: A104796 A132020 A143864 this_sequence A125165 A065489 A051672
Adjacent sequences: A073361 A073362 A073363 this_sequence A073365 A073366 A073367
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 23 2002
|
|
EXTENSIONS
|
a(10) from Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 14 2004
a(11) from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Mar 17 2004
a(12)-a(17) from John W. Layman (layman(AT)math.vt.edu), Jul 21 2004
More terms from T. D. Noe (noe(AT)sspectra.com), Oct 16 2007
|
|
|
Search completed in 0.002 seconds
|
