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A112957
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a(1) = a(2) = a(3) = 1; for n>1: a(n+3) = a(n)^2 + a(n+1)^2 + a(n+2)^2.
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2
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1, 1, 1, 3, 11, 131, 17291, 298995963, 89398586189293211, 7992107212644486930829797919966571, 63873777698404030240264509605345282496735163325301838600463378485931
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| A quadratic tribonacci sequence.
This is to A000283 as a tribonacci (A000213) is to Fibonacci. Two oddities about his 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?
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MATHEMATICA
| Join[{a=1, b=1, c=1}, Table[d=a*a+b*b+c*c; a=b; b=c; c=d, {n, 10}]] (* From Vladimir Joseph Stephan Orlovsky, Apr 19 2011 *)
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CROSSREFS
| Cf. A000213, A000283, A072878.
Sequence in context: A088075 A088076 A072878 * A057205 A121897 A067657
Adjacent sequences: A112954 A112955 A112956 * A112958 A112959 A112960
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KEYWORD
| easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Jan 02 2006; definition corrected Jan 02 2006
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