A111240 Index at which n-th prime appears in A109890.

2, 3, 9, 23, 40, 22, 67, 49, 43, 48, 58, 89, 76, 151, 98, 24, 44, 59, 185, 100, 271, 122, 207, 178, 84, 217, 130, 31, 88, 145, 357, 119, 138, 309, 123, 47, 590, 150, 334, 684, 245, 39, 139, 81, 66, 70, 253, 642, 737, 227, 50, 144, 131, 422, 496, 479, 516, 389, 715

Offset: 1

Author

N. J. A. Sloane, Oct 30 2005

Keywords

• nonn

Examples

			The 4th prime, 7, is A109890(23), so a(4) = 23.
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..1262

Crossrefs

Cf. A000040, A000720, A109890.

Programs

Maple

A109890 := proc(nmin) local a,i,k,apsum; a := [1] ; apsum := 1 ; while nops(a) < nmin do k := 1; while k in a or not ( apsum mod k = 0 or k mod apsum = 0 ) do k := k+1 ; od ; a := [op(a),k] ; apsum := apsum+k ; od; RETURN(a) ; end: A111240 := proc(nmin) local a,a109890,n,i; a := [] ; a109890 := A109890(nmin) ; n := 1; while member( ithprime(n),a109890,'i') do a := [op(a),i] ; n := n+1 ; od; RETURN(a) ; end: A111240(560) ; # R. J. Mathar, Aug 20 2007

Mathematica

nn = 1000; c[] := False; p[] := 0;
Array[Set[{a[#], c[#]}, {#, True}] &, 2];
r = 0; s = a[1] + a[2]; p[2] = 2;
Monitor[Do[k = SelectFirst[Divisors[s], ! c[#] &];
  c[k] = True;
  Map[(If[p[#] == 0, Set[p[#], n]]; If[# > r, r = #]) &,
    FactorInteger[k][[All, 1]]];
  s += k, {n, 3, nn}], n];
s = 1; Reap[While[Set[k, p[Prime[s]]] > 0, Sow[k]; s++] ][[-1, 1]] (* Michael De Vlieger, Apr 26 2024 *)

Extensions

More terms from R. J. Mathar, Aug 20 2007

More terms from David Wasserman, Jan 07 2009