The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A213183 Initialize a(1)=R=1. Repeat: copy the last R preceding terms to current position; increment R; do twice: append the least integer that has not appeared in the sequence yet. 1
 1, 1, 2, 3, 2, 3, 4, 5, 3, 4, 5, 6, 7, 4, 5, 6, 7, 8, 9, 5, 6, 7, 8, 9, 10, 11, 6, 7, 8, 9, 10, 11, 12, 13, 7, 8, 9, 10, 11, 12, 13, 14, 15, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 11, 12 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Every positive integer k occurs floor((k+3)/2) times: 1 and 2 occur twice, 3 and 4 thrice, 5 and 6 four times, and so on. LINKS EXAMPLE a(1) = 1  -- initial value a(2) = 1  -- copied one last term a(3)=2, a(4)=3  -- appended two terms a(5)=2, a(6)=3  -- copied two last terms a(7)=4, a(8)=5  -- appended two terms a(9)=3, a(10)=4, a(11)=5  -- copied three last terms a(12)=6, a(13)=7  -- appended two terms a(14)=4, a(15)=5, a(16)=6, a(17)=7  -- copied four last terms a(18)=8, a(19)=9  -- appended two terms, and so on. Comments from N. J. A. Sloane, Apr 28 2020, following a suggestion from Paul Curtz: (Start) With an initial -1, 0, this may also be regarded as a triangle read by rows:   -1;    0,  1;    1,  2,  3;    2,  3,  4,  5;    3,  4,  5,  6,  7;    4,  5,  6,  7,  8,  9;    5,  6,  7,  8,  9, 10, 11;    6,  7,  8,  9, 10, 11, 12, 13;   ... or as an array read by upward antidiagonals:   -1,  1,  3,  5,  7,  9, 11, ...    0,  2,  4,  6,  8, 10, ...    1,  3,  5,  7,  9, ...    2,  4,  6,  8, ...    3,  5,  7, ...    4,  6, ...    5, ...   ... (End) PROG (Python) a = [1]*992 R = 1 i = 2 while i<900:         for t in range(R):                 a[i] = a[i-R]                 i += 1         R += 1         a[i] = a[i-1] + 1         i += 1         a[i] = a[i-1] + 1         i += 1 for i in range(1, 99):         print(a[i], end=', ') CROSSREFS If we prefix this with -1, 0, and then add 1 to every term, we get A051162. Sequence in context: A324532 A324390 A260112 * A125929 A309236 A071933 Adjacent sequences:  A213180 A213181 A213182 * A213184 A213185 A213186 KEYWORD nonn,easy,tabf AUTHOR Alex Ratushnyak, Mar 05 2013 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 27 15:49 EDT 2021. Contains 346308 sequences. (Running on oeis4.)