A068543 Numbers k such that abs(prime(k)-k*tau(k)) < sqrt(k).

2, 3, 5, 26, 27, 33, 34, 171, 172, 175, 188, 1029, 1030, 1038, 1045, 1048, 1054, 1065, 1066, 1085, 1086, 1090, 1095, 1102, 1105, 1106, 1107, 39834, 39850, 39860, 39861, 39876, 39908, 39915, 39916, 39935, 39940, 39948, 39951, 39956, 39964, 39968

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..666

Maple

R:= NULL: count:= 0: p:= 1:
for n from 1 while count < 100 do
  p:= nextprime(p);
  if (p - n*numtheory:-tau(n))^2 < n then
    R:= R, n; count:= count+1;
  fi
od:
R; # Robert Israel, Jul 23 2025

Mathematica

Reap[For[n = 2, n <= 40000, n++, If[Abs[Prime[n] - n*DivisorSigma[0, n]] < Sqrt[n], Sow[n]]]][[2, 1]] (* Jean-François Alcover, Nov 07 2016 *)

Crossrefs

Cf. A067292.

Sequence in context: A280258 A181730 A024774 * A064026 A121264 A141566

Adjacent sequences: A068540 A068541 A068542 * A068544 A068545 A068546

Keyword

nonn

Author

Benoit Cloitre, Mar 22 2002

Status

approved