A166744 Unlucky primes: numbers which are members of both A000040 (primes) and A050505 (unlucky).

2, 5, 11, 17, 19, 23, 29, 41, 47, 53, 59, 61, 71, 83, 89, 97, 101, 103, 107, 109, 113, 131, 137, 139, 149, 157, 167, 173, 179, 181, 191, 197, 199, 227, 229, 233, 239, 251, 257, 263, 269, 271, 277, 281, 293, 311, 313, 317, 337, 347, 353, 359, 373, 379, 383, 389

Offset

1,1

Comments

There are infinitely many unlucky prime numbers, in particular all those of the form 6n - 1, eliminated in the second step of Ulam's procedure for lucky numbers. - Davide Rotondo, Aug 31 2020

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

L:= [seq(2*i+1, i=0..10^3)]:
for n from 2 while n < nops(L) do
  r:= L[n];
  L:= subsop(seq(r*i=NULL, i=1..nops(L)/r), L);
od:
U:= {2, seq(i, i=3..2*10^3+1, 2)} minus convert(L, set):
sort(convert(select(isprime, U), list)); # Robert Israel, Jul 26 2019

Prog

(SageMath)
# Copy from  A000959 - (Robert FERREOL, Nov 19 2014)
def lucky(n):
  L=list(range(1, n+1, 2)); j=1
  while L[j] <= len(L)-1:
    L=[L[i] for i in range(len(L)) if (i+1)%L[j]!=0]
    j+=1
  return(L)
[ p for p in prime_range(1000) if p not in lucky(1000) ] # Hauke Löffler, Jul 26 2019

Crossrefs

Cf. A007528, A031157 (lucky primes).

Sequence in context: A009770 A132121 A070957 * A080165 A239712 A224363

Adjacent sequences: A166741 A166742 A166743 * A166745 A166746 A166747

Keyword

nonn

Author

Gabriel Finch (salsaman(AT)xs4all.nl), Oct 21 2009

Status

approved