A307221 Positions of records in A306440.

0, 1, 6, 30, 36, 540, 2100, 3780, 15120, 37800, 85680, 120960, 126000, 131040, 196560, 302400, 332640, 786240, 917280, 1179360, 2702700, 3341520, 4324320, 8648640, 19656000, 19958400, 21205800, 43243200, 46781280, 57657600, 64864800, 122522400, 151351200

Offset: 1

Author

Robert Israel, Mar 29 2019

Keywords

• nonn

Comments

Numbers k such that A306440(k) > A306440(j) for all j < k.

Examples

			a(3) = 6 is in the sequence because A306440(6) = 2 while A306440(j) < 2 for 0 <= j < 6.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..50

Crossrefs

Cf. A306440.

Programs

Maple

A306440:= proc(n) local t;
    nops(select(t -> t^2<2*n and isprime(t+1) and isprime(2*n/t+1), numtheory:-divisors(2*n)))
end proc:
Res:= 0: vmax:= 0:
for n from 1 to 10^6 do
  v:= A306440(n);
  if v > vmax then
    Res:= Res, n; vmax:= v;
  fi
od:
Res;

Mathematica

A306440[n_] := Length[Select[Divisors[2n], #^2 < 2n && PrimeQ[#+1] && PrimeQ[2n/#+1]&]];
Res = {0}; vmax = 0;
For[n = 1, n <= 10^6 , n++, v = A306440[n]; If[v > vmax, Print[n]; AppendTo[Res, n]; vmax = v]];
Res (* Jean-François Alcover, Oct 17 2020, translated from Maple *)

Extensions

a(24)-a(33) from Daniel Suteu, Mar 29 2019