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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A321339 a(1)=1; thereafter a(n) = a(n-1) * prime(a(n-1))^(n-1).

Original entry on oeis.org

1, 2, 18, 4085658, 94856826320432984953640661130233988218
Offset: 1

Views

Author

Russell Y. Webb, Nov 05 2018

Keywords

Comments

The prime factorization of a(n) describes all previous terms in the sequence: a(n) = prime(a(1))^1 * prime(a(2))^2 * prime(a(3))^3 * ...* prime(a(n-1))^(n-1).
An infinite and monotonically increasing sequence. Grows fast enough that a(6) and later terms are too large to display in full.

Examples

			4085658 = 2 * 3^2 *61^3 = prime(1)^1 * prime(2)^2 * prime(18)^3. The previous values in the sequence can be read from this factorization: the 3rd is 18, the 2nd is 2, the 1st is 1.

Crossrefs

Somewhat similar to A007097.
Cf. A321340.

Programs

  • Mathematica
    Nest[Append[#, #[[-1]] Prime[#[[-1]] ]^Length@ #] &, {1}, 4] (* Michael De Vlieger, Nov 05 2018 *)
nxt[{n_,a_}]:={n+1,a*Prime[a]^n}; NestList[nxt,{1,1},4][[All,2]] (* Harvey P. Dale, May 28 2019 *)
  • PARI
    apply( a(n) = prod(i=1, n-1, prime(a(i))^i), [1..5] )
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