A073320 A073259(n)=3: the length of iteration transient leading to n-th composite number equals 3.

4, 5, 8, 9, 13, 16, 17, 18, 22, 23, 24, 27, 31, 35, 36, 40, 41, 46, 47, 56, 64, 69, 70, 71, 89, 90, 91, 92, 93, 94, 95, 103, 109, 110, 111, 112, 113, 146, 147, 161, 162, 163, 171, 172, 173, 174, 196, 240, 241, 242, 243, 261, 262, 263, 277, 438, 439, 440, 1137, 1138

Offset

1,1

Links

Table of n, a(n) for n=1..60.

Formula

See Program.

Example

The sequence is most probably complete. a(1)=4: the fixed point list from m=a(1) to composite[m] is: {4,7,9}, the length is 3; last term is a(64)=1142 with transient list {1142,1332,1360}.

Mathematica

lfp[x_] := Length[FixedPointList[x+PrimePi[ # ]+1&, x]]-1 Do[s=lfp[n]; If[Equal[s, 3], Print[n]], {n, 1, 10000000}]

Crossrefs

Cf. A002808, A073259.

Sequence in context: A316097 A206554 A267489 * A020668 A020934 A094004

Adjacent sequences: A073317 A073318 A073319 * A073321 A073322 A073323

Keyword

fini,full,nonn

Author

Labos Elemer, Jul 29 2002

Status

approved