login
A176888
Unsafe primes minus 1.
0
1, 2, 12, 16, 18, 28, 30, 36, 40, 42, 52, 60, 66, 70, 72, 78, 88, 96, 100, 102, 108, 112, 126, 130, 136, 138, 148, 150, 156, 162, 172, 180, 190, 192, 196, 198, 210, 222, 228, 232, 238, 240, 250, 256, 268, 270, 276, 280, 282, 292, 306, 310, 312, 316, 330, 336
OFFSET
1,2
COMMENTS
Non-semiprimes k such that k+1 is a prime.
FORMULA
a(n)=A059456(n)-1.
MATHEMATICA
Select[Prime[Range[70]]-1, PrimeOmega[#]!=2&] (* Harvey P. Dale, Jan 14 2015 *)
CROSSREFS
Sequence in context: A102975 A120300 A089021 * A114974 A298001 A071566
KEYWORD
nonn
AUTHOR
EXTENSIONS
Entries checked by R. J. Mathar, May 06 2010
STATUS
approved