A249036 a(1)=1, a(2)=2; thereafter a(n) = a(n-1-(number of even terms so far)) + a(n-1-(number of odd terms so far)).

1, 2, 2, 3, 4, 4, 5, 5, 6, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 13, 14, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 32, 33, 33, 34, 34, 35, 35, 36, 36, 37, 37, 38, 38, 39, 39, 40, 40, 41, 41, 42, 42, 43, 43, 44, 44, 45, 45, 46, 46, 47

Offset: 1

Author

N. J. A. Sloane, Oct 26 2014

Keywords

• nonn

Comments

Suggested by A006336 and A007604.

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006336, A007604.

A249037 and A249038 give numbers of even and odd terms so far.

Programs

Maple

M:=100;
v[1]:=1; v[2]:=2; w[1]:=0; w[2]:=1; x[1]:=1; x[2]:=1;
for n from 3 to M do
   v[n]:=v[n-1-w[n-1]]+v[n-1-x[n-1]];
if v[n] mod 2 = 0 then w[n]:=w[n-1]+1; x[n]:=x[n-1];
                  else w[n]:=w[n-1]; x[n]:=x[n-1]+1; fi;
od:
[seq(v[n], n=1..M)]; # A249036
[seq(w[n], n=1..M)]; # A249037
[seq(x[n], n=1..M)]; # A249038

Mathematica

Nest[Append[#, #[[Length@Select[#, OddQ]]] + #[[Length@Select[#, EvenQ]]]] &, {1, 2}, 75] (* Ivan Neretin, May 02 2016 *)