|
|
A023524
|
|
Number of distinct prime divisors of prime(n)*prime(n-1) + 1.
|
|
3
|
|
|
1, 1, 1, 2, 3, 2, 3, 2, 3, 2, 3, 3, 4, 3, 3, 3, 3, 3, 3, 4, 2, 3, 3, 2, 3, 4, 3, 4, 2, 3, 4, 4, 3, 3, 3, 3, 2, 3, 4, 3, 3, 3, 4, 2, 3, 3, 5, 3, 5, 3, 3, 2, 3, 3, 2, 4, 3, 3, 3, 3, 3, 4, 3, 3, 3, 4, 3, 3, 4, 3, 3, 4, 4, 3, 3, 4, 4, 4, 4, 6, 3, 4, 3, 2, 2, 3, 2
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,4
|
|
COMMENTS
|
|
|
LINKS
|
|
|
MAPLE
|
1, seq(nops(numtheory:-factorset(ithprime(n)*ithprime(n-1)+1)), n=2..100); # Robert Israel, Dec 22 2015
|
|
MATHEMATICA
|
Prepend[Table[PrimeNu[Prime@ n Prime[n - 1] + 1], {n, 2, 80}], 1] (* Michael De Vlieger, Dec 22 2015 *)
|
|
PROG
|
(PARI) a(n) = if (n==1, 1, omega(prime(n)*prime(n-1) + 1)); \\ Michel Marcus, Dec 22 2015
(Magma) [#PrimeDivisors((NthPrime(n)*(NthPrime(n-1))+1)): n in [1..100]]; // Vincenzo Librandi, Dec 23 2015
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|