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A309023 For n >= 1, if there exists an m < n such that a(m) = a(n), take the largest such m and set a(n+1) = (n-m)^a(n); otherwise a(n+1) = 0. Start with a(1)=1, a(2)=2. 0
1, 2, 0, 0, 1, 4, 0, 1, 3, 0, 1, 3, 27, 0, 1, 4, 10000, 0, 1, 4, 256, 0, 1, 4, 256 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence quickly generates terms of immense size.

Changing what a(n+1) is set to when a new term arises changes the sequence nontrivially.

LINKS

Table of n, a(n) for n=1..25.

MATHEMATICA

Nest[Function[{a, n}, Append[a, If[Length@ # == 0, 0, (n - #[[-1, 1]])^Last@ a] &@ Position[Most@ a, _?(# == Last@ a &)] ]] @@ {#, Length@ #} &, {1, 2}, 24] (* Michael De Vlieger, Jul 08 2019 *)

PROG

(Python)

def Prog(length):

    L = 2

    seq = [1, 2]

    while L < length:

        x = len(seq)-1

        while x > 0:

            if seq[-1] == seq[x-1]:

                m_minus_n = len(seq)-x

                a_n = seq[L-1]

                seq.append((m_minus_n)**a_n)

                x = -1

            else:

                x -= 1

            if x == 0:

                seq.append(0)

        L += 1

    return seq

CROSSREFS

Cf. A181391.

Sequence in context: A168511 A111146 A109077 * A137585 A301344 A301579

Adjacent sequences:  A309020 A309021 A309022 * A309024 A309025 A309026

KEYWORD

nonn

AUTHOR

Philip Kalisman, Jul 07 2019

STATUS

approved

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Last modified January 20 01:01 EST 2022. Contains 350467 sequences. (Running on oeis4.)