|
|
A245283
|
|
a(n) = a(n-1) * (a(n-1) + a(n-2)) / a(n-4) with a(1) = a(2) = a(3) = a(4) = 1.
|
|
2
|
|
|
1, 1, 1, 1, 2, 6, 48, 2592, 3421440, 1952520007680, 79423772100432548659200, 2433694280407609647520301298079459442688000, 1731103819002733625504286414686785477293241305893841298989509923950758461440000
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,5
|
|
LINKS
|
|
|
FORMULA
|
a(n+3) = a(n+2) * A245384(n) for n>0.
|
|
MATHEMATICA
|
a[ n_] := If[ n<5, 1, a[n] = a[n-1] (a[n-1] + a[n-2]) / a[n-4]];
RecurrenceTable[{a[n] == a[n-1]*(a[n-1] + a[n-2])/a[n-4], a[1] == a[2] == a[3] == a[4] == 1}, a, {n, 1, 10}] (* G. C. Greubel, Aug 06 2018 *)
nxt[{a_, b_, c_, d_}]:={b, c, d, d (d+c)/a}; NestList[nxt, {1, 1, 1, 1}, 15][[All, 1]] (* Harvey P. Dale, Jun 25 2021 *)
|
|
PROG
|
(PARI) {a(n) = if( n<5, 1, a(n-1) * (a(n-1) + a(n-2)) / a(n-4))};
(Magma) I:=[1, 1, 1, 1]; [n le 4 select I[n] else Self(n-1)*(Self(n-1) + Self(n-2))/Self(n-4): n in [1..10]]; // G. C. Greubel, Aug 06 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|