

A325597


a(n) is the least number not 2a(m) + a(m1) for any m < n.


5



1, 2, 3, 4, 6, 7, 9, 10, 12, 13, 14, 15, 17, 18, 19, 21, 22, 23, 24, 26, 27, 28, 30, 31, 32, 33, 35, 36, 37, 39, 40, 42, 43, 45, 46, 47, 48, 50, 51, 52, 54, 55, 57, 58, 59, 60, 62, 63, 64, 66, 67, 69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 84, 85, 86, 87
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OFFSET

1,2


COMMENTS

Conjectures: Let d(n) = 3a(n)  4n; then d(n) is bounded, and d(n) = 0 for infinitely many n.


LINKS

Clark Kimberling, Table of n, a(n) for n = 1..10000


EXAMPLE

Necessarily, a(1) = 1 and a(2) = 2. Because of these values, 5 is the least number not in the sequence, so that a(3) = 3 and a(4) = 4. Consequently, 8 and 11 are disallowed, so a(5) = 6 and a(6) = 7.


MATHEMATICA

mex[list_, start_] := (NestWhile[# + 1 &, start, MemberQ[list, #] &]); a = {1}; Do[AppendTo[a, mex[Rest[2 a] + Most[a], Last[a] + 1]], {60}]; a (* A325597 *)
c = Complement[Range[Last[a]], a] (* A325598 *)
da = Differences[a] (* A325599 *)
Flatten[Position[da, 1]] (* A325600 *)
Flatten[Position[da, 2]] (* A325601 *)
(* Peter J. C. Moses, May 07 2019 *)


CROSSREFS

Cf. A325598, A325599, A325417.
Sequence in context: A186275 A214857 A175320 * A001953 A230748 A078607
Adjacent sequences: A325594 A325595 A325596 * A325598 A325599 A325600


KEYWORD

nonn,easy


AUTHOR

Clark Kimberling, May 10 2019


STATUS

approved



