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.

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A324981 a(n) = Product_{d|n} (d*pod(d)) where pod(k) = the product of the divisors of k (A007955).

Original entry on oeis.org

1, 4, 9, 128, 25, 7776, 49, 65536, 2187, 100000, 121, 5159780352, 169, 537824, 759375, 1073741824, 289, 198359290368, 361, 512000000000, 4084101, 5153632, 529, 21035720123168587776, 78125, 11881376, 43046721, 10578455953408, 841, 15943230000000000000, 961
Offset: 1

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Author

Jaroslav Krizek, Mar 22 2019

Keywords

Examples

			a(6) = 1*pod(1) * 2*pod(2) * 3*pod(3) * 6*pod(6) = (1*1) * (2*2) * (3*3) * (6*36) = 7776.
		

Crossrefs

Cf. A007955, A174933 (Sum_{d|n} (d*pod(d))), A266265.

Programs

  • Magma
    [&*[d * &*[c: c in Divisors(d)]: d in Divisors(n)]: n in [1..100]]
    
  • Mathematica
    Array[Times @@ Map[# Apply[Times, Divisors@ #] &, Divisors@ #] &, 31] (* Michael De Vlieger, Mar 24 2019 *)
  • PARI
    a(n) = my(d=divisors(n), p=1); fordiv(n, d, p*=d*vecprod(divisors(d))); p;  \\ Michel Marcus, Mar 22 2019

Formula

a(n) = (Product_{d|n} d) * (Product_{d|n} pod(d)) = A007955(n) * A266265(n).
a(p) = p^2 for p = primes (A000040).
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