A075076 Integers pertaining to A075075: a(n) = b(n-1)*b(n+1)/b(n) where b(n) is the n-th term of A075075.

2, 3, 2, 10, 6, 4, 15, 6, 20, 12, 12, 30, 12, 28, 6, 33, 14, 7, 44, 13, 14, 34, 26, 15, 51, 18, 55, 36, 24, 55, 20, 56, 30, 30, 56, 39, 36, 68, 52, 42, 85, 40, 77, 60, 45, 77, 42, 99, 56, 56, 99, 72, 80, 54, 57, 30, 46, 38, 29, 23, 62, 58, 37, 31, 82, 74, 38, 123, 38, 86, 114, 39

Offset: 2

Author

Amarnath Murthy, Sep 09 2002

Keywords

• nonn
• look

Comments

This is not a permutation of the natural numbers since a(4)=a(2), a(9)=a(6), a(12)=a(11) etc. [From Hagen von Eitzen, May 16 2009]

Links

• Alois P. Heinz, Table of n, a(n) for n = 2..10000

Crossrefs

Cf. A075075.

Programs

Maple

c:= proc() false end:
b:= proc(n) option remember; local k, m;
       if n<3 then k:=n
     else m:= denom(b(n-2) /b(n-1));
          for k from m by m while c(k) do od
       fi;
       c(k):= true; k
    end:
a:= n-> b(n-1)*b(n+1)/b(n):
seq(a(n), n=2..100);  # Alois P. Heinz, Jul 18 2012

Mathematica

Clear[b, c]; c[] = False; b[n] := b[n] = Module[{k, m}, If[n<3, k = n, m = Denominator[b[n-2]/b[n-1]]; For[k = m, c[k], k = k+m]]; c[k] = True; k];a[n_] := b[n-1]*b[n+1]/b[n]; Table[a[n], {n, 2, 100}] (* Jean-François Alcover, Jun 10 2015, after Alois P. Heinz *)

Extensions

More terms from Sascha Kurz, Feb 03 2003