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Search: id:A118334
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| A118334 |
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a(n-1)*a(n-6) + a(n-2)*a(n-7) + a(n-3)*a(n-8) + a(n-4)*a(n-9), with a(k<8) = 1. |
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1
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| 1, 1, 1, 1, 1, 1, 1, 1, 4, 7, 13, 25, 49, 94, 463, 3691, 51649, 1342825, 67140874, 6378379789, 2959568174113, 10926725697533971, 564365382277563803725, 757844508822251885989584694, 50882343436271211095738004051924943
(list; graph; listen)
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OFFSET
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0,9
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COMMENT
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This is the 4-term analogue of the 2-term recurrence A111288 a(1) = a(2) = a(3) = a(4) = 1. For n>= 5, a(n) = a(n-1)*a(n-3) + a(n-2)*a(n-4). Primes in this sequence include a(n) for n = 9, 10, 14, 15... with a(16) through a(28) composite, a(28) has 74 digits, and the sequence growing beyond my ability to efficiently test primality.
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FORMULA
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a(0) = a(1) = a(2) = a(3) = a(4) = a(5) = a(6) = a(7) = 1; for n>7: a(n) = a(n-1)*a(n-6) + a(n-2)*a(n-7) + a(n-3)*a(n-8) + a(n-4)*a(n-9).
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CROSSREFS
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Cf. A111288, A111388.
Adjacent sequences: A118331 A118332 A118333 this_sequence A118335 A118336 A118337
Sequence in context: A039694 A000288 A074863 this_sequence A004119 A074864 A074865
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), May 14 2006
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