OFFSET
1,1
COMMENTS
Previous name was: "Product of prime-index-primes and the index of their prime index".
Sum of reciprocals converges to about 1/2. [More accurately, 0.50056748... . - Amiram Eldar, Jul 13 2024]
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = n*A006450(n). - Omar E. Pol, Oct 21 2013
EXAMPLE
a(1) = 1*prime(prime(1)) = 1*prime(2) = 1*3 = 3.
a(2) = 2*prime(prime(2)) = 2*prime(3) = 2*5 = 10.
MATHEMATICA
Table[n Prime[Prime[n]], {n, 1, 40}] (* Vincenzo Librandi, Jun 09 2016 *)
PROG
(PARI) pipxindex(n) = {sr=0; pr=1; for(x=1, n, y=prime(prime(x)); pr=x*y; print1(pr" "); sr+=1.0/pr; ); print(); print(sr) }
(Magma) [n*NthPrime(NthPrime(n)): n in [1..40]]; // Vincenzo Librandi, Jun 09 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Cino Hilliard, Mar 04 2003
EXTENSIONS
New name from Omar E. Pol, Oct 21 2013
STATUS
approved