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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A254873 Recamán [divide, -, +, *]-sequence with seed 14 and step 2. 1
14, 7, 5, 3, 1, 2, 4, 6, 8, 10, 12, 24, 22, 11, 9, 18, 16, 32, 30, 15, 13, 26, 28, 56, 54, 27, 25, 23, 21, 19, 17, 34, 36, 38, 40, 20 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Starting at the seed number (14) the sequence continues by dividing, subtracting, adding or multiplying by the step number (2). Division gets precedence over subtraction which gets precedence over addition which gets precedence over multiplication. The new number must be a positive integer and not previously listed. The sequence terminates if this is impossible.

Less chaotic sequences are obtained if division is not included (see for example A254868).

These sequences were first explored by Brian Kehrig, a 15-year-old student at Renert School, Calgary, Canada.

They are exceptionally good sequences to introduce to the elementary school math classroom.

Like many Recamán sequences, this is worth listening to.

LINKS

Table of n, a(n) for n=1..36.

EXAMPLE

a(1) = 14.  a(2) = 14/2 = 7.  a(3) = 7-2 = 5.  a(4) = 5-2 = 3.  a(5) = 3-2 = 1.  a(6) = 1*2 = 2.  a(7) = 2+2 = 4.  a(8) = 4+2 = 6.

MATHEMATICA

f[lst_List] := Block[{k = lst[[-1]]}, If[ Mod[k, 2] == 0 && !MemberQ[lst, k/2], k /= 2, If[k > 2 && !MemberQ[lst, k - 2], k -= 2, If[ !MemberQ[lst, k + 2], k += 2, k *= 2]]]; Append[lst, k]]; lst = {14}; Nest[f, lst, 70] (* Robert G. Wilson v, Feb 20 2015 *)

CROSSREFS

Cf. A254868, A005132.

Sequence in context: A033334 A161914 A162774 * A004479 A135638 A040185

Adjacent sequences:  A254870 A254871 A254872 * A254874 A254875 A254876

KEYWORD

easy,hear,nonn,fini,full

AUTHOR

Gordon Hamilton, Feb 09 2015

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 June 25 20:26 EDT 2017. Contains 288730 sequences.