A306698 Recamán-like sequence: a(0) = 0: for n > 0, a(n) = a(n-1) - 2*n if positive and not already in the sequence, otherwise a(n) = a(n-1) + n.

0, 1, 3, 6, 10, 15, 21, 7, 15, 24, 4, 15, 27, 40, 12, 27, 43, 9, 27, 46, 66, 87, 109, 63, 87, 37, 63, 90, 34, 63, 93, 31, 63, 96, 28, 63, 99, 25, 63, 102, 22, 63, 105, 19, 63, 108, 16, 63, 111, 13, 63, 114, 166, 60, 114, 169, 57, 114, 172, 54, 114, 175, 51

Offset

0,3

Comments

Conjecture: This is a surjection onto A032766.

Links

Peter Kagey, Table of n, a(n) for n = 0..10000

Laura Kuttnig, One step forward - two steps back --- Recamán Variation, Youtube video, Feb 28, 2019.

Reddit user NonEuclideanDreamer, One step forward - two steps back --- A Variation of the Recamán Sequence

Mathematica

Nest[Append[#1, If[And[#3 >= 0, FreeQ[#1, #3]], #3, Last[#1] + #2]] & @@ {#1, #2, Last[#1] - 2 #2} & @@ {#, Length@ #} &, {0}, 62] (* Michael De Vlieger, Mar 11 2019 *)

Crossrefs

Cf. A005132, A032766.

Sequence in context: A034175 A361670 A368825 * A139131 A130485 A115015

Adjacent sequences: A306695 A306696 A306697 * A306699 A306700 A306701

Keyword

nonn

Author

Peter Kagey, Mar 05 2019

Status

approved