|
| |
|
|
A051786
|
|
Propp's cubic recurrence: a(0) = a(1) = a(2) = a(3) = 1; a(n)=(1+a(n-1)*a(n-2)*a(n-3))/a(n-4).
|
|
3
| |
|
|
1, 1, 1, 1, 2, 3, 7, 43, 452, 45351, 125920291, 60027819184831, 758397193749171922281611, 126403219004744354228963383975713263866432, 45699526286117471520994956894648733172150425791690122432447239675853643
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,5
|
|
|
REFERENCES
| Jim Propp (propp(AT)math.wisc.edu), personal communication.
|
|
|
FORMULA
| a(-n)=a(3+n). a(0)=a(1)=a(2)=a(3)=1. a(n+2)*a(n-2)=1+a(n+1)*a(n)*a(n-1).
|
|
|
MATHEMATICA
| RecurrenceTable[{a[1]==a[2]==a[3]==a[4]==1, a[n]==(1+a[n-1]a[n-2]a[n-3])/ a[n-4]}, a[n], {n, 15}] (* From Harvey P. Dale, May 14 2011 *)
|
|
|
PROG
| (PARI) {a(n)= if(n<0, n=3-n); if(n<4, 1, (a(n-1)*a(n-2)*a(n-3)+1)/a(n-4)) } /* Michael Somos Oct 16 2006 */
|
|
|
CROSSREFS
| Cf. A005246.
Sequence in context: A000946 A091771 A072714 * A133400 A113845 A072713
Adjacent sequences: A051783 A051784 A051785 * A051787 A051788 A051789
|
|
|
KEYWORD
| nonn,nice,easy
|
|
|
AUTHOR
| Michael Somos
|
|
|
EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion of Andrew Plewe, Jun 17 2007
|
| |
|
|
