A110809 a(1) = 3, a(2n) = a(2n-1)*(a(2n-1)+1)/2, a(2n+1) = a(2n)*(a(2n)-1)/2.

3, 6, 15, 120, 7140, 25493370, 324955944231765, 52798182845779144865989623495, 1393824055908163580110066696496417846029512708072933195765, 971372749414141756744711053350258180262238679505115309556108472465628097348257583700704919225793663496284373565495

Offset

1,1

Comments

a(10) has 114 digits; a(11) has 228 digits. - Emeric Deutsch, Oct 06 2005

Links

Table of n, a(n) for n=1..10.

Maple

a:=proc(n) if n=1 then 3 elif n mod 2 = 0 then a(n-1)*(a(n-1)+1)/2 else a(n-1)*(a(n-1)-1)/2 fi end: seq(a(n), n=1..10); # Emeric Deutsch, Oct 06 2005

Crossrefs

Sequence in context: A280992 A013270 A013276 * A013275 A013271 A013272

Adjacent sequences: A110806 A110807 A110808 * A110810 A110811 A110812

Keyword

easy,nonn

Author

Amarnath Murthy, Aug 14 2005

Extensions

More terms from Emeric Deutsch, Oct 06 2005

Status

approved