|
Search: id:A087612
|
|
|
| A087612 |
|
A divisibility sequence derived from Lehmer's polynomial x^10+x^9-x^7-x^6-x^5-x^4-x^3+x+1. Square root of the terms in A059928. |
|
+0
2
|
|
| 1, 1, 1, 3, 1, 1, 1, 3, 1, 1, 1, 9, 1, 13, 29, 3, 1, 1, 37, 3, 1, 23, 1, 9, 49, 25, 1, 39, 1, 29, 32, 93, 67, 1, 71, 27, 1, 37, 79, 3, 83, 13, 173, 69, 29, 47, 1, 423, 293, 49, 103, 75, 317, 53, 109, 39, 37, 59, 1297, 261, 367, 1024, 1, 93, 1, 1541, 269, 201, 277, 923, 283, 1917
(list; graph; listen)
|
|
|
OFFSET
|
1,4
|
|
|
COMMENT
|
The sequence is conjectured to contain an infinite number of primes. The first 100 terms contain 33 unique primes. As stated by Everest and Ward, except for a finite number of composite n, a(n) can be prime only if n is prime. For this sequence, n=23*47 is the largest composite for which a(n) is prime.
|
|
REFERENCES
|
See A059928
|
|
LINKS
|
G. Everest and T. Ward, Primes in Divisibility Sequences
|
|
MATHEMATICA
|
CompanionMatrix[p_, x_] := Module[{cl=CoefficientList[p, x], deg, m}, cl=Drop[cl/Last[cl], -1]; deg=Length[cl]; If[deg==1, {-cl}, m=RotateLeft[IdentityMatrix[deg]]; m[[ -1]]=-cl; Transpose[m]]]; c=CompanionMatrix[x^10+x^9-x^7-x^6-x^5-x^4-x^3+x+1, x]; im=IdentityMatrix[10]; tmp=im; Table[tmp=tmp.c; Sqrt[Abs[Det[tmp-im]]], {n, 100}]
|
|
CROSSREFS
|
Cf. A059928.
Adjacent sequences: A087609 A087610 A087611 this_sequence A087613 A087614 A087615
Sequence in context: A069292 A091842 A060901 this_sequence A051997 A086869 A095345
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
T. D. Noe (noe(AT)sspectra.com), Sep 15 2003
|
|
|
Search completed in 0.002 seconds
|
