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.
%I A297002 #15 Sep 24 2018 08:54:58 %S A297002 1,3,7,9,13,21,19,27,49,39,29,63,37,57,91,81,43,147,53,117,133,87,61, %T A297002 189,169,111,343,171,71,273,79,243,203,129,247,441,89,159,259,351,101, %U A297002 399,107,261,637,183,113,567,361,507,301,333,131,1029,377,513,371 %N A297002 Completely multiplicative with a(prime(k)) = prime(2 * k) (where prime(k) denotes the k-th prime). %C A297002 This sequence is a permutation of {1} union A066207. %C A297002 This sequence is the third row of A248601. %H A297002 Rémy Sigrist, <a href="/A297002/b297002.txt">Table of n, a(n) for n = 1..10000</a> %F A297002 a(n) = A248601(3, n) for any n > 0. %t A297002 Array[Times @@ Map[Power @@ # &, FactorInteger[#] /. {p_, e_} /; p > 1 :> {Prime[2 PrimePi@ p], e}] &, 57] (* _Michael De Vlieger_, Dec 23 2017 *) %o A297002 (PARI) a(n) = my (f=factor(n)); prod(i=1, #f~, prime(2 * primepi(f[i,1]))^f[i,2]) %Y A297002 Cf. A066207, A248601. %K A297002 easy,nonn,mult %O A297002 1,2 %A A297002 _Rémy Sigrist_, Dec 23 2017 %E A297002 Comment corrected by _Rémy Sigrist_, Sep 22 2018