A209430 Denominator of l(n), where l(1)=1, l(2)=2, l(n)=l(n-1)+2*l(n-2)/n.

1, 1, 3, 3, 15, 45, 315, 315, 2835, 14175, 155925, 467775, 6081075, 42567525, 58046625, 638512875, 10854718875, 97692469875, 1856156927625, 9280784638125, 194896477400625, 2143861251406875, 49308808782358125, 147926426347074375, 217538862275109375, 4370553505709015625

Offset

1,3

References

Szekeres, G. The average value of skew Hadamard matrices. Proceedings of the First Australian Conference on Combinatorial Mathematics (Univ. Newcastle, Newcastle, 1972), pp. 55--59. Univ. of Newcastle Res. Associates, Newcastle, 1972. MR0349708 (50 #2201)

Links

G. C. Greubel, Table of n, a(n) for n = 1..500

Example

1, 2, 8/3, 11/3, 71/15, 268/45, 2302/315, 2771/315, 29543/2835, 172654/14175, 2194624/155925, 7533469/467775, 111102841/6081075, 875654984/42567525, ...

Mathematica

Denominator[RecurrenceTable[{a[1]==1, a[2]==2, a[n]==a[n-1]+(2a[n-2])/n}, a, {n, 30}]] (* Harvey P. Dale, Mar 30 2014 *)

Crossrefs

Cf. A209429, A052127.

Sequence in context: A280781 A046983 A067655 * A160624 A049606 A046126

Adjacent sequences: A209427 A209428 A209429 * A209431 A209432 A209433

Keyword

nonn,frac

Author

N. J. A. Sloane, Mar 22 2012

Status

approved