A120610 Sum of previous term and preceding non-divisors.

2, 3, 5, 10, 13, 33, 63, 126, 187, 442, 869, 1753, 3506, 5257, 12269, 24538, 36805, 85876, 171755, 343507, 687019, 1374038, 2061055, 4809126, 9618252, 14427378, 28854567, 62518388, 125036840, 250073665, 500147342, 1000294687, 2000589376

Offset

1,1

Links

Michael De Vlieger, Table of n, a(n) for n = 1..3428

Formula

a(1) = 2, a(2) = 3, for n>=2, a(n+1) = a(n) + sum_{1<=k<n, a(k) does not divide a(n)} a(k).

Mathematica

s={2, 3}; Do[sum=s[[-1]]; Do[If[!Divisible[s[[-1]], s[[j]]], sum=sum+s[[j]] ], {j, k-1}]; AppendTo[s, sum] , {k, 2, 32}]; s (* James C. McMahon, Oct 07 2024 *)

Crossrefs

Cf. A120611.

Sequence in context: A071848 A268176 A120938 * A090859 A004681 A338589

Adjacent sequences: A120607 A120608 A120609 * A120611 A120612 A120613

Keyword

nonn

Author

Franklin T. Adams-Watters, Jun 16 2006

Status

approved