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A171947 P-positions for game of UpMark. 3
1, 3, 7, 9, 11, 15, 19, 23, 25, 27, 31, 33, 35, 39, 41, 43, 47, 51, 55, 57, 59, 63, 67, 71, 73, 75, 79, 83, 87, 89, 91, 95, 97, 99, 103, 105, 107, 111, 115, 119, 121, 123, 127, 129, 131, 135, 137, 139, 143, 147, 151, 153, 155, 159, 161, 163, 167, 169, 171, 175, 179 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The following description, due to D. R. Hofstadter, Email, Oct 23 2014, is presumably equivalent to Fraenkel's. Begin with 1, and then each new member is 2k-1, where k is the smallest unused non-member of the sequence.  Thus k starts out as 2, so 2k-1 = 3, so 3 is the sequence's second member.  The next value of k is 4, giving 2k-1 = 7, so 7 is the sequence's third member.  Then k = 5, so 9 is the next member.  Then k = 6, so 11 is the next member.  Then k = 8, so 15 is the next member.  Etc.  - N. J. A. Sloane, Oct 26 2014

LINKS

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

Aviezri S. Fraenkel, The vile, dopey, evil and odious game players,  Discrete Math. 312 (2012), no. 1, 42-46.

FORMULA

Presumably equal to 2*A003159 + 1. - Reinhard Zumkeller, Oct 26 2014

MAPLE

# Maple code for M+1 terms of sequence, from N. J. A. Sloane, Oct 26 2014

m:=1; a:=[m]; M:=100;

for n from 1 to M do

m:=m+1; if m in a then m:=m+1; fi;

c:=2*m-1;

a:=[op(a), c];

od:

[seq(a[n], n=1..nops(a))];

PROG

(Haskell)

import Data.List (delete)

a171947 n = a171947_list !! (n-1)

a171947_list = 1 : f [2..] where

   f (w:ws) = y : f (delete y ws) where y = 2 * w - 1

-- Reinhard Zumkeller, Oct 26 2014

CROSSREFS

Complement of A171946. Essentially identical to A072939.

A249034 gives missing odd numbers.

Cf. A003159.

Sequence in context: A047529 A125667 A072939 * A186890 A248667 A075607

Adjacent sequences:  A171944 A171945 A171946 * A171948 A171949 A171950

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Oct 29 2010

STATUS

approved

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Last modified December 21 02:15 EST 2014. Contains 252291 sequences.