login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A093802 Number of distinct factorizations of 105*2^n. 3
5, 15, 36, 74, 141, 250, 426, 696, 1106, 1711, 2593, 3852, 5635, 8118, 11548, 16231, 22577, 31092, 42447, 57464, 77213, 103009, 136529, 179830, 235514, 306751, 397506, 512607, 658030, 841020, 1070490, 1357195, 1714274, 2157539, 2706174, 3383187, 4216358 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..300

EXAMPLE

105*A000079 is 105, 210, 420, 840, 1680, 3360, ...and there are 15 distinct factorizations of 210 so a(1) = 15.

a(0) = 5: 105*2^0 = 105 = 3*5*7 = 3*35 = 5*21 = 7*15. - Alois P. Heinz, May 26 2013

MAPLE

with(numtheory):

b:= proc(n, k) option remember;

      `if`(n>k, 0, 1) +`if`(isprime(n), 0,

      add(`if`(d>k, 0, b(n/d, d)), d=divisors(n) minus {1, n}))

    end:

a:= n-> b((105*2^n)$2):

seq(a(n), n=0..50);  # Alois P. Heinz, May 26 2013

CROSSREFS

Similar sequences: 45*A000079 => A002763, [1, 3, 9, 27, 81, 243...]*A000079 => A054225, 1*A002110 => A000110, 2*A002110 => A035098, A000142 => A076716.

Cf. A001055, A126442, A129306.

Sequence in context: A174655 A184631 A011933 * A006008 A325952 A086716

Adjacent sequences:  A093799 A093800 A093801 * A093803 A093804 A093805

KEYWORD

easy,nonn

AUTHOR

Alford Arnold, May 19 2004

EXTENSIONS

2 more terms from Alford Arnold, Aug 29 2007

Corrected offset and extended beyond a(7) by Alois P. Heinz, May 26 2013

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 2 06:37 EST 2021. Contains 341744 sequences. (Running on oeis4.)