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A087559 Rearrangement of natural numbers such that n*a(n) + 1 is a prime. 3
1, 2, 4, 3, 6, 5, 10, 9, 8, 7, 18, 13, 12, 14, 16, 15, 24, 11, 22, 20, 26, 19, 30, 17, 28, 21, 34, 25, 32, 23, 36, 29, 40, 27, 42, 31, 48, 39, 38, 33, 56, 35, 46, 47, 50, 43, 44, 37, 52, 45, 60, 49, 66, 54, 58, 41, 68, 55, 62, 51, 70, 59, 74, 67, 86, 53, 64, 57, 72, 61, 98, 69 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
k pertaining to A111296. {A111296(n)-1}/n.
If a(n) = m then a(m) = n.
a(a(n)) = n; a(A131221(n)) = A131221(n). - Reinhard Zumkeller, Jun 18 2007
LINKS
MAPLE
s := {seq(i, i=2..2000)}:a[1] := 1:for n from 2 to 120 do l := sort(convert(s, list)): k := 1: while(not isprime(n*l[k]+1)) do k := k+1: if(k>nops(l)) then print("Overflow"):fi:od: a[n] := l[k]:s := s minus {a[n]}:od:seq(a[l], l=1..120); # Sascha Kurz
MATHEMATICA
l = {}; Do[k = 1; While[MemberQ[l, k] || !PrimeQ[n*k + 1], k++ ]; AppendTo[l, k], {n, 100}]; l (* Ryan Propper, Jun 15 2006 *)
CROSSREFS
Cf. A111296.
Sequence in context: A132340 A132666 A116533 * A193298 A168007 A359114
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Sep 13 2003
EXTENSIONS
More terms from Sascha Kurz, Sep 22 2003
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 09 2007
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)