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A177211 Numbers k that are the products of two distinct primes such that 2*k-1 and 4*k-3 are also products of two distinct primes. 11
33, 118, 119, 134, 146, 226, 247, 249, 287, 295, 334, 335, 386, 391, 393, 395, 422, 478, 493, 497, 502, 519, 551, 583, 589, 614, 629, 634, 694, 697, 721, 731, 749, 755, 789, 802, 817, 843, 879, 898, 955, 958, 985, 989, 1003, 1037, 1079, 1114, 1154, 1159, 1177 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
33 is a term because 33 = 3*11, 2*33 - 1 = 65 = 5*13 and 2*65 - 1 = 4*33 - 3 = 129 = 3*43.
MATHEMATICA
f[n_]:=Last/@FactorInteger[n]=={1, 1}; lst={}; Do[If[f[n]&&f[2*n-1]&&f[4*n-3], AppendTo[lst, n]], {n, 0, 7!}]; lst
tdpQ[n_]:=PrimeNu[n]==PrimeOmega[n]==PrimeNu[2n-1]==PrimeOmega[2n-1] == PrimeNu[4n-3]==PrimeOmega[4n-3]==2; Select[Range[1200], tdpQ] (* Harvey P. Dale, Nov 15 2020 *)
CROSSREFS
Sequence in context: A044284 A044665 A140161 * A337626 A301633 A039440
KEYWORD
nonn
AUTHOR
EXTENSIONS
Definition clarified by Harvey P. Dale, Nov 15 2020
STATUS
approved

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Last modified March 28 11:46 EDT 2024. Contains 371241 sequences. (Running on oeis4.)