The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A081330 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A081330

Numbers that can be written as sum of two 3-smooth numbers.
(history; published version)

#19 by Michel Marcus at Sun Sep 10 05:55:10 EDT 2017

STATUS

reviewed

approved

#18 by Joerg Arndt at Sun Sep 10 05:12:49 EDT 2017

STATUS

proposed

reviewed

#17 by Michel Marcus at Sun Sep 10 04:31:26 EDT 2017

STATUS

editing

proposed

#16 by Michel Marcus at Sun Sep 10 04:31:20 EDT 2017

LINKS

Ivars Peterson, <a href="http://www.sciencenews.org/sn_arc99/1_23_99/mathland.htm">Medieval Harmony</a>. [Broken link]

STATUS

proposed

editing

#15 by Jean-François Alcover at Sun Sep 10 04:22:13 EDT 2017

STATUS

editing

proposed

#14 by Jean-François Alcover at Sun Sep 10 04:22:08 EDT 2017

MATHEMATICA

max = 100; Table[2^i *3^j + 2^k* 3^l, {i, 0, Log[2, max] // Ceiling}, {j, 0, Log[3, max] // Ceiling}, {k, 0, Log[2, max] // Ceiling}, {l, 0, Log[3, max] // Ceiling}] // Flatten // Union // Select[#, # <= max &] & (* Jean-François Alcover, Sep 10 2017 *)

STATUS

approved

editing

#13 by Charles R Greathouse IV at Sun Sep 07 00:46:21 EDT 2014

STATUS

editing

approved

#12 by Charles R Greathouse IV at Sun Sep 07 00:46:13 EDT 2014

PROG

(PARI) list(lim)=my(v=List(), u=v, N); for(n=0, log(lim\1+.5)\log(3), N=3^n; while(N<=lim, listput(v, N); N<<=1)); v=Set(v); for(i=1, #v, for(j=i, #v, N=v[i]+v[j]; if(N>lim, break); listput(u, N))); Set(u) \\ Charles R Greathouse IV, Sep 07 2014

STATUS

approved

editing

#11 by Joerg Arndt at Sat Sep 06 02:31:00 EDT 2014

STATUS

editing

approved

#10 by Charles R Greathouse IV at Fri Sep 05 08:23:05 EDT 2014

COMMENTS

A081326(a(n)) > 0; complement of A081329.

FORMULA

a(n) >> exp(n^(1/4)) [_. - _Charles R Greathouse IV_, Aug 22 2011]

STATUS

approved

editing