A378189 Positions of records in A205561.

1, 3, 5, 7, 13, 17, 37, 83, 137, 173, 193, 269, 311, 479, 607, 673, 1019, 1427, 1523, 1613, 3391, 3527, 4817, 5021, 5623, 9887, 14891, 15823, 21701, 22727, 24439, 26399, 27581, 28771, 29339, 35491, 37967, 49207, 51157, 52639, 54799, 64303, 93077, 104323, 115279, 116981, 117881, 135209, 157177

Offset

1,2

Comments

Numbers m such that there is k such that for every m' < m, there exist j and k' such that 1 <= j < k' <= k and m' divides (2*k')! - (2*j)!, but there do not exist j and k' such that 1 <= j < k' <= k and m divides (2*k')! - (2*j)!.

Links

Robert Israel, Table of n, a(n) for n = 1..113

Maple

f:= proc(n) local S, j, x;
  S:= {}:
  x:= 1:
  for j from 1 do
    x:=x*2*j*(2*j-1) mod n;
    if member(x, S) then return j fi;
    S:= S union {x}
  od
end proc:
J:= 1: m:= 2: count:= 1:
for k from 2 while count < 70 do
  v:= f(k);
  if v > m then J:= J, k; count:= count+1; m:= v;
  fi
od:
J;

Crossrefs

Cf. A205561, A378188.

Sequence in context: A066464 A062324 A194829 * A226794 A300748 A173641

Adjacent sequences: A378186 A378187 A378188 * A378190 A378191 A378192

Keyword

nonn

Author

Robert Israel, Nov 19 2024

Status

approved