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A189313 Primes p such that 2*omega(4p) = omega(4p+2), where omega(k) is the number of distinct primes dividing k, A001221. 2
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 (list; graph; refs; listen; history; text; internal format)
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 *)

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

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Last modified August 25 21:00 EDT 2019. Contains 326324 sequences. (Running on oeis4.)