A073439 Numbers k such that A073259(k)=4: the length of iteration-transient leading to k-th composite number equals 4.

1, 2, 3, 6, 7, 10, 11, 12, 14, 15, 19, 20, 21, 25, 26, 28, 30, 32, 33, 34, 37, 38, 39, 42, 44, 45, 48, 49, 50, 51, 53, 54, 55, 57, 58, 59, 61, 62, 63, 65, 66, 67, 68, 72, 73, 74, 75, 77, 78, 81, 82, 84, 85, 86, 87, 88, 96, 97, 98, 100, 101, 102, 104, 106, 107, 108, 114, 116, 117, 118, 119, 120, 121, 122, 123, 124, 126, 127, 129, 130, 131, 132, 134, 135, 136, 137, 140, 141, 142, 143, 144, 145, 148

Offset

1,2

Links

Sean A. Irvine, Table of n, a(n) for n = 1..4662

Example

The sequence is probably finite and given in full. a(1)=1: the fixed point list from m=a(1) to composite[m] is: {1,2,3,4}, the length is 4; largest term seems to be a(4662)=77629, with transient list {77629,85259,85933,85990}. The terms appears in bursts of consecutive integers. A chain of 37 consecutive numbers starts at 28046.

Mathematica

lfp[x_] := Length[FixedPointList[x+PrimePi[ # ]+1&, x]]-1 Do[s=lfp[n]; If[Equal[s, 4], Print[n]], {n, 1, 10000000}]

Crossrefs

Cf. A002808, A073259, A073320.

Sequence in context: A208892 A085397 A307414 * A188084 A242750 A299239

Adjacent sequences: A073436 A073437 A073438 * A073440 A073441 A073442

Keyword

nonn,changed

Author

Labos Elemer, Jul 31 2002

Extensions

Offset corrected by Sean A. Irvine, Nov 28 2024

Status

approved