cp's OEIS Frontend

A343021 Positions of records in A343016.

%I A343021 #13 Apr 14 2021 01:17:59
%S A343021 1,2,6,90,15120,983010
%N A343021 Positions of records in A343016.
%C A343021 Numbers k such that A343016(k) > A343016(j) for all j < k.
%C A343021 a(n) is divisible by 6 for n >= 3, by 30 for n >= 4, by 210 for n >= 5.
%C A343021 a(7) > 10^9 if it exists.
%e A343021 A343016(1) = 0.
%e A343021 A343016(2) = 1 is the first value > 0 in A343016.
%e A343021 A343016(6) = 5 is the first value > 1.
%e A343021 A343016(90) = 6 is the first value > 5.
%e A343021 A343016(15120) = 7 is the first value > 6.
%e A343021 A343016(983010) = 8 is the first value > 7.
%p A343021 R:= 1,2:
%p A343021 vmax:= 2:
%p A343021 f:= proc(n) local s, t, k;
%p A343021   s:= add(t[1]*t[2], t = ifactors(n)[2]);
%p A343021   for k from 0 do if not isprime(k*n+s) then return k fi od;
%p A343021 end proc:
%p A343021 for n from 6 by 6 to 10^6 do
%p A343021   v:= f(n);
%p A343021   if v > vmax then
%p A343021     vmax:= v;
%p A343021     R:= R, n;
%p A343021   fi
%p A343021 od:
%p A343021 R;
%t A343021 With[{s = Array[Block[{m = 0, k = Plus @@ Times @@@ FactorInteger[#]}, While[PrimeQ[# m + k], m++]; m] &, 10^6]}, Map[FirstPosition[s, #][[1]] &, Union@ FoldList[Max, s]]] (* _Michael De Vlieger_, Apr 13 2021 *)
%Y A343021 Cf. A343016.
%K A343021 nonn,more
%O A343021 1,2
%A A343021 _J. M. Bergot_ and _Robert Israel_, Apr 02 2021