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A112957 a(1) = a(2) = a(3) = 1; for n > 1, a(n+3) = a(n)^2 + a(n+1)^2 + a(n+2)^2. 6
1, 1, 1, 3, 11, 131, 17291, 298995963, 89398586189293211, 7992107212644486930829797919966571, 63873777698404030240264509605345282496735163325301838600463378485931 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
A quadratic tribonacci sequence.
This is to A000283 as a tribonacci (A000213) is to Fibonacci. Two oddities about this sequence: (a) its first 7 terms are identical to terms numbered 2 through 8 of A072878; (b) only one of the first 9 terms are composite. Primes in the sequence begin 3, 11, 131, 17291 and 89398586189293211. What is the next prime?
LINKS
MATHEMATICA
Join[{a=1, b=1, c=1}, Table[d=a*a+b*b+c*c; a=b; b=c; c=d, {n, 10}]] (* Vladimir Joseph Stephan Orlovsky, Apr 19 2011 *)
CROSSREFS
Sequence in context: A276258 A284604 A072878 * A057205 A121897 A067657
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Jan 02 2006; definition corrected Jan 02 2006
STATUS
approved

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Last modified March 19 07:31 EDT 2024. Contains 370955 sequences. (Running on oeis4.)