|
%I #14 Jul 25 2021 10:56:27
%S 1,4,9,20,35,66,91,136,171,230,319,372,481,574,645,752,901,1062,1159,
%T 1340,1491,1606,1817,1992,2225,2522,2727,2884,3103,3270,3503,4064,
%U 4323,4658,4865,5364,5587,5966,6357,6680,7093,7518,7783,8404,8685,9062,9353
%N n times the n-th noncomposite.
%C Does some n > 2 exist such that n * prime(n-1) / (n + prime(n-1)), i.e. a(n) / A090178(n) is an integer?
%C Complement of A171519. - _Jaroslav Krizek_, Dec 13 2009
%C Partial sums of A092929. - _Gionata Neri_, May 26 2015
%H Charles R Greathouse IV, <a href="/A164931/b164931.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = n*A008578(n).
%t Module[{nn=200,cmps},cmps=Select[Range[nn],!CompositeQ[#]&];Times@@@ Thread[ {cmps,Range[Length[cmps]]}]] (* _Harvey P. Dale_, Jul 25 2021 *)
%o (PARI) a(n)=if(n>1,n*prime(n-1),1) \\ _Charles R Greathouse IV_, Jun 02 2015
%K nonn,easy
%O 1,2
%A _Jaroslav Krizek_, Aug 31 2009
%E Correction for change of offset in A008578 by _Jaroslav Krizek_, Jan 27 2010
|
