A209429 Numerator of l(n), where l(1)=1, l(2)=2, l(n)=l(n-1)+2*l(n-2)/n.

1, 2, 8, 11, 71, 268, 2302, 2771, 29543, 172654, 2194624, 7533469, 111102841, 875654984, 1335478594, 16332117629, 307026528761, 3040884758542, 63303287929996, 345404844856129, 7886534621278669, 94005382576044068, 2335627560917144282, 7547413632563686237, 11923476834093824801

Offset

1,2

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

Numerator[RecurrenceTable[{a[1] == 1, a[2] == 2, a[n] == a[n - 1] + (2 a[n - 2])/n}, a, {n, 50}]] (* G. C. Greubel, Jan 02 2018 *)

Crossrefs

Cf. A209430, A052127.

Sequence in context: A093918 A332098 A254313 * A135132 A178060 A007543

Adjacent sequences: A209426 A209427 A209428 * A209430 A209431 A209432

Keyword

nonn,frac

Author

N. J. A. Sloane, Mar 22 2012

Status

approved