A140524 a(1)=2. For n >=2, a(n) = the least integer >= n that is non-coprime to both n and a(n-1).

2, 2, 6, 4, 10, 6, 14, 8, 12, 10, 22, 12, 26, 14, 18, 16, 34, 18, 38, 20, 24, 22, 46, 24, 30, 26, 30, 28, 58, 30, 62, 32, 36, 34, 40, 36, 74, 38, 42, 40, 82, 42, 86, 44, 48, 46, 94, 48, 56, 50, 54, 52, 106, 54, 60, 56, 60, 58, 118, 60, 122, 62, 66, 64, 70, 66, 134, 68, 72, 70

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

f:= proc(n) option remember; local k, v;
  v:= procname(n-1);
  for k from n do if igcd(k, n) > 1 and igcd(k, v) > 1 then return k fi
  od:
end proc:
f(1):= 2:
map(f, [$1..100]); # Robert Israel, Mar 07 2018

Mathematica

a = {2}; Do[ i = n; While[ Min[ GCD[ a[ [ -1 ] ], i ], GCD[ n, i ] ] == 1, i++ ]; AppendTo[ a, i ], {n, 2, 60} ]; a (* Stefan Steinerberger, Aug 04 2008 *)

Crossrefs

Sequence in context: A284918 A053213 A292258 * A204904 A109043 A054585

Adjacent sequences: A140521 A140522 A140523 * A140525 A140526 A140527

Keyword

nonn

Author

Leroy Quet, Jul 02 2008

Extensions

More terms from Stefan Steinerberger, Aug 04 2008

a(61)-a(70) from Ray Chandler, Jun 25 2009

Status

approved