This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A160258 #6 May 13 2017 14:20:22
%S A160258 8,12,16,18,20,24,24,27,28,30,32,32,36,36,36,40,40,42,44,45,48,48,48,
%T A160258 48,50,52,54,54,56,56,60,60,60,60,63,64,64,64,66,68,70,72,72,72,72,72,
%U A160258 72,75,76,78,80,80,80,80,81,84,84,84,84,88,88,90,90,90,90,92,96,96,96,96,96,96
%N A160258 The entries of A033942, repeated for each different factorization into 3 factors larger than 1.
%C A160258 This is the sequence of volumes for parallelepiped or rhombic hexahedron figurate numbers. Avoiding the use of 1 as a factor keeps from mentioning degenerate triples of the form 1*y*z or 1*1*z. This sequence lists products where only a volume expression will do.
%D A160258 John H. Conway and Richard K. Guy, The book of numbers, Copernicus 1996, ISBN: 038797993X
%D A160258 Peter Pearce and Susan Pearce, Polyhedra primer, Van Nostrand Reinhold, 1978, ISBN 0442264968.
%e A160258 For n=1, its mention of 8 is the sole mention because 2*2*2 is the sole distinct producing triple for 8. 2*2*2 is the 1st possible triple not using 1.
%e A160258 At indices n=13 to 15, 3*3*4, 2*3*6, and 2*2*9 all give rise to 36.
%p A160258 A001222 := proc(n) numtheory[bigomega](n) ; end:
%p A160258 isA033942 := proc(n) RETURN(A001222(n) >= 3) ; end:
%p A160258 A160258rep := proc(a,minf) local c,d,f,ct ; c := [] ; for d in numtheory[divisors](a) do if d >= minf then if d = a then c := [op(c),[d]] ; ; else ct := A160258rep(a/d,d) ; for f in ct do c := [op(c),[d,op(f)] ] ; od: fi; fi; od: c; end:
%p A160258 A160258 := proc(a) local c,r,f ; c := 0 ; r := A160258rep(a,2) ; for f in r do if nops(f) = 3 then c := c+1 ; fi; od: c ; end:
%p A160258 for n from 1 to 120 do if isA033942(n) then mu := A160258(n) ; for m from 1 to mu do printf("%d,",n) ; od; fi; od: # _R. J. Mathar_, May 12 2009
%K A160258 nonn
%O A160258 1,1
%A A160258 Chris G. Spies-Rusk (chaosorder4(AT)gmail.com), May 06 2009
%E A160258 Edited and extended by _R. J. Mathar_, May 12 2009