cp's OEIS Frontend

A224866 Numbers of the form m*rad(m)+1, where rad = A007947 (squarefree kernel).

%I A224866 #15 Jul 31 2022 07:45:54
%S A224866 2,5,9,10,17,26,28,33,37,50,65,73,82,101,109,122,126,129,145,170,197,
%T A224866 201,217,226,244,257,289,290,325,344,362,393,401,433,442,485,501,513,
%U A224866 530,577,626,649,676,677,730,785,801,842,865,901,962,969,973,1001
%N A224866 Numbers of the form m*rad(m)+1, where rad = A007947 (squarefree kernel).
%C A224866 A078310 in natural order.
%H A224866 Reinhard Zumkeller, <a href="/A224866/b224866.txt">Table of n, a(n) for n = 1..10000</a>
%F A224866 a(n) = A001694(n) + 1.
%t A224866 powQ[n_] := n == 1 || AllTrue[FactorInteger[n][[;; , 2]], # > 1 &]; Select[Range[1001], powQ[# - 1] &] (* _Amiram Eldar_, Jul 31 2022 *)
%o A224866 (Haskell)
%o A224866 a224866 n = a224866_list !! (n-1)
%o A224866 a224866_list = [x | x <- [2..] , let x' = x - 1, let k = a007947 x',
%o A224866                     let (y,m) = divMod x' k, m == 0, a007947 y == k]
%o A224866 (PARI) is(n) = n>1 && ispowerful(n-1) \\ _Charles R Greathouse IV_, Aug 08 2013, corrected by _Amiram Eldar_, Jul 31 2022
%Y A224866 Subsequences: A078325, A078324.
%Y A224866 Cf. A001694, A078310, A007947.
%K A224866 nonn
%O A224866 1,1
%A A224866 _Reinhard Zumkeller_, Jul 23 2013