Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #15 Jul 31 2022 07:45:54
%S 2,5,9,10,17,26,28,33,37,50,65,73,82,101,109,122,126,129,145,170,197,
%T 201,217,226,244,257,289,290,325,344,362,393,401,433,442,485,501,513,
%U 530,577,626,649,676,677,730,785,801,842,865,901,962,969,973,1001
%N Numbers of the form m*rad(m)+1, where rad = A007947 (squarefree kernel).
%C A078310 in natural order.
%H Reinhard Zumkeller, <a href="/A224866/b224866.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A001694(n) + 1.
%t powQ[n_] := n == 1 || AllTrue[FactorInteger[n][[;; , 2]], # > 1 &]; Select[Range[1001], powQ[# - 1] &] (* _Amiram Eldar_, Jul 31 2022 *)
%o (Haskell)
%o a224866 n = a224866_list !! (n-1)
%o a224866_list = [x | x <- [2..] , let x' = x - 1, let k = a007947 x',
%o let (y,m) = divMod x' k, m == 0, a007947 y == k]
%o (PARI) is(n) = n>1 && ispowerful(n-1) \\ _Charles R Greathouse IV_, Aug 08 2013, corrected by _Amiram Eldar_, Jul 31 2022
%Y Subsequences: A078325, A078324.
%Y Cf. A001694, A078310, A007947.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Jul 23 2013