id:A099812 - OEIS Search Results

Search: id:A099812

Displaying 1-1 of 1 results found.

page 1

Number of distinct primes dividing 2n (i.e. omega(2n)).

+0
1

1, 1, 2, 1, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 3, 1, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 1, 3, 2, 3, 2, 2, 2, 3, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 3, 2, 2, 3, 2, 2, 3, 1, 3, 3, 2, 2, 3, 3, 2, 2, 2, 2, 3, 2, 3, 3, 2, 2, 2, 2, 2, 3, 3, 2, 3, 2, 2, 3, 3, 2, 3, 2, 3, 2, 2, 2, 3, 2, 2, 3, 2, 2, 4 (list; graph; listen)

	OFFSET	`1,3`
	EXAMPLE	`a(6)=2 because 12=223 has 2 distinct prime divisors; a(15)=3 because 30=235 has 3 distinct prime divisors.`
	MAPLE	`with(numtheory): omega:=proc(n) local div, A, j: div:=divisors(n): A:={}: for j from 1 to tau(n) do if isprime(div[j])=true then A:=A union {div[j]} else A:=A fi od: nops(A) end: seq(omega(2*n), n=1..130); (Deutsch)`
	CROSSREFS	`Bisection of A001221.` `Cf. A001221, A092523.` `Sequence in context: A083952 A043529 A080942 this_sequence A068068 A092505 A066086` `Adjacent sequences: A099809 A099810 A099811 this_sequence A099813 A099814 A099815`
	KEYWORD	`nonn,easy`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), Nov 19 2004`
	EXTENSIONS	`More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 10 2005`

page 1

Search completed in 0.002 seconds

Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

AT&T Labs Research