A280327 a(n) is obtained by applying the map k -> composite(k) n times, starting at n.

4, 12, 25, 39, 60, 94, 133, 183, 236, 320, 415, 520, 640, 805, 1007, 1212, 1463, 1800, 2144, 2562, 3021, 3523, 4135, 4840, 5747, 6630, 7701, 9057, 10392, 11812, 13519, 15400, 17534, 19827, 22564, 25624, 29206, 32998, 37041, 41819, 46659, 53223, 59345, 66104, 73368, 81897, 91157, 100827, 112045

Offset: 1

Author

Matthew Campbell, Dec 31 2016

Keywords

• nonn

Examples

			a(3) is 25 because the third composite is 8, the eighth composite is 15, and for the 3rd iteration, the fifteenth composite is 25.
To get a(4): 4 -> 9 -> 16 -> 26 -> 39.
		

Crossrefs

Cf. A002808.

For primes, see A058009.

Programs

Mathematica

c = Select[Range[10^6], CompositeQ]; Table[Nest[c[[#]] &, n, n], {n, 50}] (* Michael De Vlieger, Dec 31 2016 *)

Extensions

More terms from Michael De Vlieger, Dec 31 2016