A136033 a(n) = smallest number k such that number of prime factors of 2^k-1 is exactly n (counted with multiplicity).

2, 4, 6, 16, 12, 18, 24, 40, 54, 36, 102, 110, 60, 72, 108, 140, 120, 156, 144, 200, 216, 210, 240, 180, 456, 288, 336, 300, 396, 480, 882, 360, 468, 700

Offset

1,1

Links

Table of n, a(n) for n=1..34.

Maple

N:= 24: # to get a(1) to a(N)
unknown:= N:
for k from 2 while unknown > 0 do
  q:= numtheory:-bigomega(2^k-1);
  if q <= N and not assigned(A[q]) then
     A[q]:= k;
     unknown:= unknown - 1;
  fi
od:
seq(A[i], i=1..N); # Robert Israel, Oct 24 2014

Prog

(PARI) a(n) = {k = 1; while(bigomega(2^k-1) != n, k++); k; } \\ Michel Marcus, Nov 04 2013

Crossrefs

Cf. A000225, A003260, A016047, A046051, A049479, A088863, A136030, A136031.

Sequence in context: A127679 A049022 A209867 * A343019 A355594 A357172

Adjacent sequences: A136030 A136031 A136032 * A136034 A136035 A136036

Keyword

nonn,more,hard

Author

Artur Jasinski, Dec 11 2007

Extensions

a(15)-a(20) from Michel Marcus, Nov 04 2013

a(21)-a(24) from Derek Orr, Oct 23 2014

a(25)-a(34) from Jinyuan Wang, Jun 07 2019

Status

approved