A022935 a(n) = a(n-1) + c(n-1) for n >= 2, a( ) increasing, given a(1)=3, where c( ) is complement of a( ).

3, 4, 6, 11, 18, 26, 35, 45, 57, 70, 84, 99, 115, 132, 151, 171, 192, 214, 237, 261, 286, 313, 341, 370, 400, 431, 463, 496, 530, 566, 603, 641, 680, 720, 761, 803, 846, 890, 936, 983, 1031, 1080, 1130, 1181, 1233, 1286, 1340, 1395, 1451, 1509

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

Complement means that c(i) is the i-th member of the sorted list of integers >=1 that are not in the set {a(1),...,a(i-1)}. - R. J. Mathar, Aug 06 2015

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Programs

Mathematica

mex := First[Complement[Range[1, Max[#1] + 1], #1]] &;
a[1] = 3; c[1] = 1; c[2] = 2;
a[n_] := a[n] = a[n - 1] + c[n - 1];
c[n_] := c[n] = mex[Flatten[Table[{a[i], c[i]}, {i, 1, n - 1}]]];
Table[a[n], {n, 80}]  (* A022935 *)
Table[c[n], {n, 80}]
(* Clark Kimberling, May 15 2012 *)