A079150 Primes p such that p+1 has at most 3 prime factors, counted with multiplicity; i.e., primes p such that bigomega(p+1) = A001222(p+1) <= 3.
2, 3, 5, 7, 11, 13, 17, 19, 29, 37, 41, 43, 61, 67, 73, 97, 101, 109, 113, 137, 157, 163, 173, 181, 193, 211, 229, 241, 257, 277, 281, 283, 313, 317, 331, 337, 353, 373, 397, 401, 409, 421, 433, 457, 523, 541, 547, 577, 601, 613, 617, 641, 653, 661, 673, 677
Offset: 1
Examples
173 is in the sequence because 173+1 = 2*3*29 has 3 prime factors.
Links
- Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Select[Prime[Range[200]],PrimeOmega[#+1]<4&] (* Harvey P. Dale, Feb 02 2012 *)
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PARI
s(n) = {sr=0; ct=0; forprime(x=2,n, if(bigomega(x+1) < 4, print1(x" "); sr+=1.0/x; ct+=1; ); ); print(); print(ct" "sr); } \\ Lists primes p<=n such that p+1 has at most 3 prime factors.