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A363100
Fractal sequence which is left unchanged by interleaving it with the natural numbers, in such a way that each term k of the sequence is followed by the next k not-yet-seen natural numbers.
0
1, 2, 2, 3, 4, 2, 5, 6, 3, 7, 8, 9, 4, 10, 11, 12, 13, 2, 14, 15, 5, 16, 17, 18, 19, 20, 6, 21, 22, 23, 24, 25, 26, 3, 27, 28, 29, 7, 30, 31, 32, 33, 34, 35, 36, 8, 37, 38, 39, 40, 41, 42, 43, 44, 9, 45, 46, 47, 48, 49, 50, 51, 52, 53, 4, 54
OFFSET
1,2
COMMENTS
a(1) = 1. Each term a(n) = k is followed by the k smallest so-far-unseen natural numbers. Invented by Eric Angelini. Another way to say it (Angelini's formulation) is that when subjected to an erasure transformation, the k terms after a(n) = k are deleted, the original sequence is recovered; and if otherwise unconstrained, the natural numbers are introduced as soon as possible.
CROSSREFS
Sequence in context: A208521 A209570 A205703 * A367467 A333937 A325785
KEYWORD
nonn,easy
AUTHOR
Allan C. Wechsler, May 20 2023
STATUS
approved