|
Search: id:A117157
|
|
|
| A117157 |
|
a(1)=a(2)=1; a(n)=a(n-1)*a(n-2)+a(n-3)+a(n-4)+...a(1) for n>2. |
|
+0
2
|
|
| 1, 1, 1, 2, 4, 11, 49, 548, 26872, 14725925, 395715057217, 5827270253948278214, 2305938581960065033611659323852, 13437327306087560724405450621249967248150551970959
(list; graph; listen)
|
|
|
OFFSET
|
1,4
|
|
|
COMMENT
|
Form the product of the previous two terms, and then add all other previous terms.
|
|
MATHEMATICA
|
f[s_] := Block[{}, Append[s, s[[ -1]]s[[ -2]] + Plus @@ Drop[s, -2]]]; Nest[f, {1, 1}, 12] (from Robert G. Wilson v (rgwv(at)rgwv.com), May 26 2006)
|
|
PROGRAM
|
#include <stdio.h> #include <inttypes.h> int main (void) { int64_t n1=1; int64_t n2=1; int i; int64_t sum=0, next; printf("%lld, %lld, ", n1, n2); for (i=0; i<10; i++) { next=n1*n2+sum; sum+=n1; n1=n2; n2=next; printf("%lld, ", n2); } }
(PARI) {m=14; print1(a=1, ", ", b=1, ", "); v=[]; for(n=3, m, print1(k=a*b+sum(j=1, #v, v[j]), ", "); v=concat(v, a); a=b; b=k)} - (Klaus Brockhaus)
|
|
CROSSREFS
|
Cf. A117030.
Sequence in context: A091240 A068488 A096119 this_sequence A057857 A091233 A007903
Adjacent sequences: A117154 A117155 A117156 this_sequence A117158 A117159 A117160
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Gabriel Finch (salsaman(AT)xs4all.nl), Apr 21 2006
|
|
EXTENSIONS
|
a(13) and a(14) from Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Apr 27 2006
|
|
|
Search completed in 0.002 seconds
|
