The sequence whose definition is: "t is the first, fourth, eleventh, ... letter of this sentence." The first few values are 1, 4, 11, 16, 24, 29, 33, 35, 39, ... (OEIS A005224).
Aronson's Sequence
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References
Hofstadter, D. R. Metamagical Themas: Questing of Mind and Pattern. New York: BasicBooks, p. 44, 1985.Sloane, N. J. A. Sequence A005224/M3406 in "The On-Line Encyclopedia of Integer Sequences."Referenced on Wolfram|Alpha
Aronson's SequenceCite this as:
Weisstein, Eric W. "Aronson's Sequence." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/AronsonsSequence.html