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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 Harvey P. Dale, Table of n, a(n) for n = 1..1000 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 Cf. A006881, A177210 Sequence in context: A044284 A044665 A140161 * A337626 A301633 A039440 Adjacent sequences:  A177208 A177209 A177210 * A177212 A177213 A177214 KEYWORD nonn AUTHOR Vladimir Joseph Stephan Orlovsky, May 04 2010 EXTENSIONS Definition clarified by Harvey P. Dale, Nov 15 2020 STATUS approved

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Last modified December 6 12:38 EST 2021. Contains 349563 sequences. (Running on oeis4.)