A107390 Composite Fibonacci sequence: each term is the composite with index equal to the sum of the previous two terms.

4, 6, 18, 36, 76, 147, 285, 532, 984, 1795, 3237, 5793, 10293, 18168, 31887, 55709, 96926, 167972, 290136, 499615, 857947, 1469576, 2511369, 4282663, 7289002, 12383250, 21002336, 35564859, 60136917, 101547211, 171253466, 288461204

Offset

1,1

Comments

What is the value of lim_{n -> infinity} a(n)/a(n+1)? - Ryan Propper, Jan 11 2007

Links

Table of n, a(n) for n=1..32.

Formula

a(n) = A002808(a(n-1) + a(n-2)); a(1)=4, a(2)=6.

Example

a(5) = A002808(18 + 36) = A002808(54) = 76.

Mathematica

Composite[n_Integer] := FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; a = 4; b = 6; Do[c = Composite[a + b]; Print[c]; a = b; b = c, {n, 100}] (* Ryan Propper, Jan 11 2007 *)

Crossrefs

Cf. A002808, A000045, A107327.

Sequence in context: A218898 A088810 A005199 * A051253 A175955 A303526

Adjacent sequences: A107387 A107388 A107389 * A107391 A107392 A107393

Keyword

nonn,easy

Author

Christopher M. Tomaszewski (cmt1288(AT)comcast.net), May 24 2005

Extensions

More terms from Ryan Propper, Jan 11 2007

Status

approved