A022941 - OEIS

A022941

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

1, 2, 5, 9, 15, 22, 30, 40, 51, 63, 76, 90, 106, 123, 141, 160, 180, 201, 224, 248, 273, 299, 326, 354, 383, 414, 446, 479, 513, 548, 584, 621, 659, 698, 739, 781, 824, 868, 913, 959, 1006, 1054, 1103, 1153, 1205, 1258, 1312, 1367, 1423, 1480, 1538

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

OFFSET

1,2

COMMENTS

Except for a(2), identical to A022940. - Ivan Neretin, Apr 05 2016

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

MAPLE

a[1]:=1: a[2]:=2: c[1]:=3: for n from 2 to 70 do c[n]:=c[n-1]+1: for k from 1 to n do if(c[n]<=a[k])then if(c[n]=a[k])then c[n]:=c[n]+1: fi: break: fi: od: a[n+1]:=a[n]+c[n-1]: od: seq(a[n], n=1..70); # Nathaniel Johnston, May 01 2011

MATHEMATICA

Fold[Append[#1, #1[[-1]] + Complement[Range[Max@#1 + 1], #1][[#2]]] &, {1, 2}, Range[50]] (* Ivan Neretin, Apr 04 2016 *)

PROG

(Haskell)

import Data.List (delete)

a022941 n = a022941_list !! (n-1)

a022941_list = 1 : 2 : f 2 [3..] where

f x (z:zs) = y : f y (delete y zs) where y = x + z

-- Reinhard Zumkeller, May 17 2013

CROSSREFS

Cf. A143344 (first differences), A156031.

Cf. A005228 and references therein.