A297002 Completely multiplicative with a(prime(k)) = prime(2 * k) (where prime(k) denotes the k-th prime).

1, 3, 7, 9, 13, 21, 19, 27, 49, 39, 29, 63, 37, 57, 91, 81, 43, 147, 53, 117, 133, 87, 61, 189, 169, 111, 343, 171, 71, 273, 79, 243, 203, 129, 247, 441, 89, 159, 259, 351, 101, 399, 107, 261, 637, 183, 113, 567, 361, 507, 301, 333, 131, 1029, 377, 513, 371

Offset: 1

Author

Rémy Sigrist, Dec 23 2017

Keywords

• easy
• nonn
• mult

Comments

This sequence is a permutation of {1} union A066207.

This sequence is the third row of A248601.

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A066207, A248601.

Programs

Mathematica

Array[Times @@ Map[Power @@ # &, FactorInteger[#] /. {p_, e_} /; p > 1 :> {Prime[2 PrimePi@ p], e}] &, 57] (* Michael De Vlieger, Dec 23 2017 *)

PARI

a(n) = my (f=factor(n)); prod(i=1, #f~, prime(2 * primepi(f[i,1]))^f[i,2])

Formula

a(n) = A248601(3, n) for any n > 0.

Extensions

Comment corrected by Rémy Sigrist, Sep 22 2018