A249039 - OEIS

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A249039

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

3

1, 2, 4, 7, 11, 17, 26, 37, 52, 70, 92, 120, 157, 200, 254, 323, 401, 490, 597, 719, 859, 1021, 1211, 1438, 1687, 1979, 2325, 2740, 3183, 3704, 4262, 4863, 5553, 6350, 7201, 8174, 9216, 10336, 11545, 12894, 14350, 15928, 17646, 19526, 21596, 23893, 26352, 29060, 32060, 35406, 39167

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Suggested by A006336, A007604 and A249036-A249038.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

For n > 1: a(n+1) = a(n) + a(n - A249040(n)) + a(n - A249041(n)) by mutual recursion. - Reinhard Zumkeller, Nov 11 2014

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]+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)]; # A249039

[seq(w[n], n=1..M)]; # A249040

[seq(x[n], n=1..M)]; # A249041

PROG

(Haskell)

import Data.List (genericIndex)

a249039 n = genericIndex a249039_list (n - 1)

a249039_list = 1 : 2 : f 2 2 1 1 where

f x u v w = y : f (x + 1) y (v + 1 - mod y 2) (w + mod y 2)

where y = u + a249039 (x - v) + a249039 (x - w)

-- Reinhard Zumkeller, Nov 11 2014

CROSSREFS

Cf. A006336, A007604, A249036, A249037, A249038.

A249040 and A249041 give numbers of even and odd terms so far.

Sequence in context: A194805 A084842 A289177 * A342492 A280962 A096967

Adjacent sequences: A249036 A249037 A249038 * A249040 A249041 A249042

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Oct 26 2014

STATUS

approved