login
This site is supported by donations to The OEIS Foundation.

 

Logo

Invitation: celebrating 50 years of OEIS, 250000 sequences, and Sloane's 75th, there will be a conference at DIMACS, Rutgers, Oct 9-10 2014.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A077563 Number of partitions into two parts which have different prime signatures. 3
0, 0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 5, 4, 4, 5, 6, 4, 8, 6, 8, 6, 8, 8, 11, 7, 10, 10, 12, 10, 12, 10, 13, 10, 15, 12, 15, 10, 17, 16, 17, 13, 18, 16, 18, 16, 19, 18, 21, 13, 20, 19, 25, 20, 23, 19, 24, 20, 25, 24, 27, 19, 24, 26, 28, 21, 28, 25, 30, 26, 31, 26, 32, 19, 30, 30, 33, 30 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,7

COMMENTS

The 'prime signature' of n is the sorted list of exponents in the prime factorization of n.

Does lim n->infinity a(n)/n exist? If not, what are the limsup and liminf of a(n)/n?

LINKS

Table of n, a(n) for n=0..76.

EXAMPLE

a(9) = 3; the partitions are 8+1, 6+3 and 5+4.

MATHEMATICA

sig[n_] := Sort[Last/@FactorInteger[n]]; a[n_] := Length[Select[Range[Floor[n/2]], sig[ # ]!=sig[n-# ]&]]

CROSSREFS

Cf. A077564.

Sequence in context: A005851 A237121 A139821 * A055256 A029147 A228571

Adjacent sequences:  A077560 A077561 A077562 * A077564 A077565 A077566

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Nov 11 2002

EXTENSIONS

Edited by Dean Hickerson, Nov 11 2002

STATUS

approved

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

Content is available under The OEIS End-User License Agreement .

Last modified July 25 02:45 EDT 2014. Contains 244897 sequences.