id:A129138 - OEIS Search Results

Search: id:A129138

Displaying 1-1 of 1 results found.

page 1

a(n) = number of positive divisors of n that are <= phi(n), where phi(n) = A000010(n).

+0
2

1, 1, 1, 2, 1, 2, 1, 3, 2, 2, 1, 4, 1, 2, 3, 4, 1, 4, 1, 4, 3, 2, 1, 6, 2, 2, 3, 4, 1, 5, 1, 5, 3, 2, 3, 7, 1, 2, 3, 6, 1, 5, 1, 4, 5, 2, 1, 8, 2, 4, 3, 4, 1, 6, 3, 6, 3, 2, 1, 9, 1, 2, 5, 6, 3, 5, 1, 4, 3, 6, 1, 10, 1, 2, 5, 4, 3, 5, 1, 8, 4, 2, 1, 9, 3, 2, 3, 6, 1, 9, 3, 4, 3, 2, 3, 10, 1, 4, 5, 7, 1, 5, 1, 6 (list; graph; listen)

	OFFSET	`1,4`
	LINKS	`Leroy Quet, Home Page (listed in lieu of email address)`
	EXAMPLE	`phi(16) = 8. So a(16) is the number of divisors of 16 which are <= 8. There are 4 such divisors: 1, 2, 4, 8; so a(16) = 4.`
	MAPLE	`with(numtheory): a:=proc(n) local div, ct, j: div:=divisors(n): ct:=0: for j from 1 to tau(n) do if div[j]<=phi(n) then ct:=ct+1 else ct:=ct: fi od: ct; end: seq(a(n), n=1..135); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 31 2007`
	CROSSREFS	`Cf. A129139, A126131, A074919.` `Sequence in context: A033273 A034836 A001055 this_sequence A112970 A112971 A050379` `Adjacent sequences: A129135 A129136 A129137 this_sequence A129139 A129140 A129141`
	KEYWORD	`nonn`
	AUTHOR	`Leroy Quet, Mar 30 2007`
	EXTENSIONS	`More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 31 2007`

page 1

Search completed in 0.002 seconds

Last modified November 25 08:46 EST 2009. Contains 167481 sequences.

AT&T Labs Research