OFFSET
1,1
COMMENTS
Factorize n to its full extent into the list 1, 2, 3, 2*2, 5, 2*3, 7, 2*2*2, 3*3, 2*5, 11, 2*2*3,..
Remove delimiting commas and the multiplication signs and build new products by pairing construction, all but the first term are in A001358.
LINKS
Ivan Neretin, Table of n, a(n) for n = 1..10000
MAPLE
pflat := proc(nmax) local a, ifs, n, p, c ; a := [1] ; for n from 2 to nmax do ifs := ifactors(n)[2] ; for p in ifs do q := op(1, p) ; for c from 1 to op(2, p) do a := [op(a), q] ; od: od: od: a ; end: pL := pflat(120) : for n from 1 to nops(pL)-2 by 2 do printf("%d, ", op(n, pL)*op(n+1, pL)) ; od: # R. J. Mathar, Aug 21 2008
MATHEMATICA
ps = Flatten[Table[ConstantArray[#[[1]], #[[2]]] & /@ FactorInteger[n], {n, 68}]]; a = ps[[Range[l = Length[ps]/2]*2 - 1]]*ps[[Range[l]*2]] (* Ivan Neretin, May 29 2015 *)
CROSSREFS
KEYWORD
nonn,less
AUTHOR
Juri-Stepan Gerasimov, Aug 17 2008
EXTENSIONS
Edited and corrected by R. J. Mathar, Aug 21 2008
STATUS
approved