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A307221 Positions of records in A306440. 1
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 (list; graph; refs; listen; history; text; internal format)
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-Fran├žois Alcover, Oct 17 2020, translated from Maple *)

CROSSREFS

Cf. A306440.

Sequence in context: A062515 A316532 A325374 * A062268 A067879 A334900

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

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Last modified May 18 23:41 EDT 2021. Contains 344009 sequences. (Running on oeis4.)