A176888 - OEIS

%I #7 Dec 29 2024 21:20:43

%S 1,2,12,16,18,28,30,36,40,42,52,60,66,70,72,78,88,96,100,102,108,112,

%T 126,130,136,138,148,150,156,162,172,180,190,192,196,198,210,222,228,

%U 232,238,240,250,256,268,270,276,280,282,292,306,310,312,316,330,336

%N Unsafe primes minus 1.

%C Non-semiprimes k such that k+1 is a prime.

%F a(n) = A059456(n) - 1.

%F a(n) ~ n log n. - _Charles R Greathouse IV_, Dec 29 2024

%t Select[Prime[Range[70]]-1,PrimeOmega[#]!=2&] (* _Harvey P. Dale_, Jan 14 2015 *)

%o (PARI) is(n)=isprime(n+1) && !isprime(n\2) \\ _Charles R Greathouse IV_, Dec 29 2024

%Y Intersection of A006093 and A100959.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Apr 28 2010

%E Entries checked by _R. J. Mathar_, May 06 2010