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A036761 Number of refactorable integers (A033950) of binary order (A029837) n. +0
4
1, 1, 0, 1, 2, 2, 4, 8, 13, 22, 39, 77, 137, 254, 459, 889, 1665, 3175, 6041, 11619, 22319, 42979 (list; graph; listen)
OFFSET

0,5

COMMENT

Since for any epsilon d[ n ]<=n^epsilon if n is large enough, a[ n ] does not grow too fast.

FORMULA

di[ x_ ] := Divisors[ x ]; ldi[ x_ ] := Length[ Divisors[ x ] ]; md[ x_ ] := MemberQ[ di[ x ], ldi[ x ] ] is used to form counting program line.

EXAMPLE

{1} has binary order 0, {2} has binary order 1, no term has binary order 2, {8} has binary order 3, {9,12} have binary order 4, {18,24} have binary order 5,...

The 8 numbers, between 63 and 128 (with binary order 7) which are divided by d(x) (A000005) are 72,80,84,88,96,104,108,128, so a[ 7 ]=8.

CROSSREFS

A000005, A033950.

Sequence in context: A079092 A039941 A104700 this_sequence A042979 A000018 A075126

Adjacent sequences: A036758 A036759 A036760 this_sequence A036762 A036763 A036764

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu)

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Last modified December 10 12:37 EST 2009. Contains 170569 sequences.


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