OFFSET
1,2
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = n + A001221(n).
a(n) = n + 1 if and only if n is prime or a power of a prime (that is, n > 1 is in A000961). - Alonso del Arte, Nov 17 2016
EXAMPLE
a(40) = 42, since 40 has two distinct prime divisors (2 and 5), and so 40 + 2 = 42.
a(41) = 42 also, since 41 is prime and therefore 41 + 1 = 42.
a(42) = 45, since 42 has three distinct prime divisors (2, 3, 7), and so 42 + 3 = 45.
MATHEMATICA
Table[n + PrimeNu[n], {n, 80}] (* Harvey P. Dale, Jun 22 2015 *)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Sep 13 2013
STATUS
approved