login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A064388 Variation (3) on Recamán's sequence (A005132): set s (the step size) initially equal to 2; to get a(n), we first try to subtract s from a(n-1): a(n) = a(n-1)-s if positive and not already in the sequence, in which case we change s to s+1; if not, a(n) = a(n-1)+s+i, where i >= 0 is the smallest number such that a(n-1)+s+i has not already appeared and now we change s to s+i+1 4
1, 3, 6, 2, 7, 13, 20, 12, 21, 11, 22, 10, 23, 9, 24, 8, 25, 43, 62, 42, 63, 41, 18, 44, 17, 45, 16, 46, 15, 47, 14, 48, 83, 119, 82, 120, 81, 121, 80, 38, 84, 37, 85, 36, 86, 35, 87, 34, 88, 33, 89, 32, 90, 31, 91, 30, 92, 29, 93, 28, 94, 27, 95, 26, 96, 167, 239, 166, 240 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Variation (4) (A064389) is the nicest of these variations.

I would also like to get the following sequences: number of steps before n appears (or 0 if n never appears), list of numbers that never appear, height of n (cf. A064288, A064289, A064290), etc.

LINKS

Table of n, a(n) for n=1..69.

Index entries for sequences related to Recamán's sequence

PROG

(BASIC)

rem Chipmunk BASIC v3.6.4(b8) http://www.nicholson.com/rhn/basic/

max=1000 : dim a(max)

s=2 : z=1 : a(z)=1 : print str$(z)+", ";

for n=1 to 200

x=z-s : if x <= 0 then goto yyy

if a(x)=0 then a(x)=1 : print str$(x)+", "; : s=s+1 : z=x : goto xxx

yyy: for i=0 to max

x=z+s+i

if a(x)=0 then a(x)=1 : print str$(x)+", "; : s=s+i+1 : z=x : goto xxx

next i

xxx: next n

print : end

rem Jeremy Gardiner, Feb 22 2014

CROSSREFS

Cf. A005132, A046901, A064387, A064389.

Sequence in context: A274648 A277558 A005132 * A064387 A064389 A118201

Adjacent sequences:  A064385 A064386 A064387 * A064389 A064390 A064391

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Sep 28 2001

EXTENSIONS

More terms from David Wasserman, Jul 16 2002

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified May 22 21:40 EDT 2017. Contains 286906 sequences.