A189313 Primes p such that 2*omega(4p) = omega(4p+2), where omega(k) is the number of distinct primes dividing k, A001221.

2, 97, 127, 157, 199, 227, 241, 277, 307, 313, 331, 367, 379, 397, 409, 457, 467, 487, 547, 617, 619, 643, 647, 709, 727, 739, 757, 773, 787, 797, 829, 877, 883, 907, 967, 977, 1033, 1039, 1069, 1087, 1117, 1123, 1171, 1193, 1237, 1249, 1277, 1291, 1297, 1303

Offset

1,1

Comments

Except for p=2, omega(4p) = 2, so except for the initial 2, these are the primes p such that omega(4p+2) = 4.

Links

G. C. Greubel, Table of n, a(n) for n = 1..1100

Mathematica

Select[Range[1000], PrimeQ[#] && 2*PrimeNu[4 #] == PrimeNu[4 # + 2] &] (* T. D. Noe, Apr 21 2011 *)
Select[Prime[Range[300]], 2*PrimeNu[4#]==PrimeNu[4#+2]&] (* Harvey P. Dale, Aug 28 2022 *)

Prog

(PARI) forprime(p=2, 1400, if(2*omega(4*p)=omega(4*p+2), print1(p", ")))

Crossrefs

Cf. A001221, A189314 (nonprime version of this sequence).

Sequence in context: A132206 A139884 A297423 * A042151 A233192 A065592

Adjacent sequences: A189310 A189311 A189312 * A189314 A189315 A189316

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 19 2011

Status

approved