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

1,3

Comments

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

Links

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

Example

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

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 *)

Crossrefs

Cf. A306440.

Sequence in context: A062515 A316532 A325374 * A351844 A345265 A062268

Adjacent sequences: A307218 A307219 A307220 * A307222 A307223 A307224

Keyword

nonn

Author

Robert Israel, Mar 29 2019

Extensions

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

Status

approved