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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A126850 a(n) = OrdinaryUnitarySigma(a(n-1)). 1
 2, 3, 4, 7, 8, 15, 24, 60, 168, 480, 1512, 3360, 12096, 28448, 64512, 163760, 401760, 991872, 2399040, 6858000, 13999104, 32752000, 69400800, 172186560, 517867392, 1666990080, 5662137600, 14475575296, 33946612000, 73359820800, 158022774000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS FORMULA a(n)= A107749(a(n-1)). - R. J. Mathar, Jun 15 2008 MAPLE A034448 := proc(n) local ifs, d ; if n = 1 then 1; else ifs := ifactors(n)[2] ; mul(1+ op(1, op(d, ifs))^op(2, op(d, ifs)), d=1..nops(ifs)) ; fi ; end: A006519 := proc(n) local i ; for i in ifactors(n)[2] do if op(1, i) = 2 then RETURN( op(1, i)^op(2, i) ) ; fi ; od: RETURN(1) ; end: A107749 := proc(n) local p2 ; p2 := A006519(n) ; numtheory[sigma](p2)*A034448(n/p2) ; end: A126850 := proc(n) option remember ; if n = 1 then 2; else A107749(A126850(n-1)) ; fi ; end: seq(A126850(n), n=1..40) ; # R. J. Mathar, Jun 15 2008 CROSSREFS Cf. A107749, A126849. Cf. A107749, A126849, A007497. Sequence in context: A120611 A092063 A227007 * A007497 A126882 A239973 Adjacent sequences:  A126847 A126848 A126849 * A126851 A126852 A126853 KEYWORD nonn AUTHOR Yasutoshi Kohmoto, Feb 24 2007 EXTENSIONS Edited and extended by R. J. Mathar, Jun 15 2008 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.

Last modified March 28 07:59 EDT 2020. Contains 333079 sequences. (Running on oeis4.)