cp's OEIS Frontend

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.

A290104 a(n) = A003963(n) / A290103(n).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 3, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 1, 4, 3, 1, 1, 1, 4, 1, 1, 2, 1, 1, 1, 1, 1, 4, 1, 3, 1, 1, 1, 1, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 1, 8, 1, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 4, 2, 3, 1, 1, 1, 1, 2, 1, 1, 4, 1, 1, 2, 1, 1, 2, 3, 1, 4, 1, 1, 1
Offset: 1

Views

Author

Antti Karttunen, Aug 13 2017

Keywords

Comments

The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k). Then a(n) is the product divided by the LCM of the integer partition with Heinz number n. - Gus Wiseman, Aug 01 2018

Examples

			n = 21 = 3 * 7 = prime(2) * prime(4), thus A003963(21) = 2*4 = 8, while A290103(21) = lcm(2,4) = 4, so a(21) = 8/4 = 2.
		

Crossrefs

Differs from A290106 for the first time at n=21.

Programs

  • Mathematica
    Table[If[n == 1, 1, Apply[Times, Map[PrimePi[#1]^#2 & @@ # &, #]] / Apply[LCM, PrimePi[#[[All, 1]] ]]] &@ FactorInteger@ n, {n, 120}] (* Michael De Vlieger, Aug 14 2017 *)
  • Scheme
    (define (A290104 n) (/ (A003963 n) (A290103 n)))

Formula

a(n) = A003963(n) / A290103(n).
Other identities. For all n >= 1:
a(A181819(n)) = A005361(n)/A072411(n).