OFFSET
0,1
LINKS
J. Bamberg, G. Cairns and D. Kilminster, The crystallographic restriction, permutations and Goldbach's conjecture, Amer. Math. Monthly, 110 (March 2003), 202-209.
MATHEMATICA
a080737[1] = a080737[2] = 0; a080737[p_?PrimeQ] := a080737[p] = p - 1; a080737[n_] := a080737[n] = If[Length[fi = FactorInteger[n]] == 1, EulerPhi[n], Total[a080737 /@ (fi[[All, 1]]^fi[[All, 2]])]]; orders = Table[{n, a080737[n]}, {n, 1, 2*10^6}]; row[0] = {1, 2}; row[n_] := Select[orders, 2*n - 1 <= #[[2]] <= 2*n &][[All, 1]]; Table[ row[n] // Last, {n, 0, 27}] (* Jean-François Alcover, Jul 24 2013 *)
PROG
(Haskell)
a080742 n k = a080742_list !! n
a080742_list = map last a080738_tabf -- Reinhard Zumkeller, Jun 13 2012
CROSSREFS
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Mar 08 2003
EXTENSIONS
Corrected and extended by Vladeta Jovovic, Mar 09 2003
STATUS
approved