Search: id:A109383
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%I A109383
%S A109383 112,120,162,300,304,378,392,396,408,520,552,567,592,612,630,656,675,
%T A109383 680,688,696,700,750,780,918,924,944,952,980,990,1044,1100,1116,1136,
%U A109383 1140,1160,1168,1170,1242,1264,1272,1300,1323,1352,1372,1380,1386,1416,
               1470
%N A109383 5-almost primes of the form semiprime + 1.
%F A109383 a(n) is in this sequence iff a(n) is in A014614 and (a(n)-1) is in A001358.
%e A109383 a(1) = 112 because (3*37)+1 = (2^4) * 7 = 112.
%e A109383 a(2) = 120 because (7*17)+1 = (2^3) * 3 * 5 = 120.
%e A109383 a(3) = 162 because (7*23)+1 = 2 * (3^4) = 162.
%e A109383 a(4) = 300 because (13*23)+1 = (2^2) * 3 * (5^2) = 300.
%e A109383 a(5) = 304 because (3*101)+1 = (2^4) * 19 = 304.
%e A109383 a(6) = 378 because (13*29)+1 = 2 * (3^3) * 7 = 378.
%t A109383 f[n_] := Plus @@ Last /@ FactorInteger[n];Select[Range[1500], f[ # ] 
               == 5 && f[ # - 1] == 2 &] (*Chandler*)
%Y A109383 Primes are in A000040. Semiprimes are in A001358. 5-almost primes are 
               in A014614.
%Y A109383 Primes of the form semiprime + 1 are in A005385 (safe primes).
%Y A109383 Semiprimes of the form semiprime + 1 are in A109373.
%Y A109383 3-almost primes of the form semiprime + 1 are in A109067.
%Y A109383 4-almost primes of the form semiprime + 1 are in A109287.
%Y A109383 5-almost primes of the form semiprime + 1 are in this sequence.
%Y A109383 Least n-almost prime of the form semiprime + 1 are in A128665.
%Y A109383 Cf. A077065, A079148, A092307.
%Y A109383 Sequence in context: A010032 A129947 A096680 this_sequence A036301 A117723 
               A157662
%Y A109383 Adjacent sequences: A109380 A109381 A109382 this_sequence A109384 A109385 
               A109386
%K A109383 easy,nonn
%O A109383 1,1
%A A109383 Jonathan Vos Post (jvospost3(AT)gmail.com), Aug 25 2005
%E A109383 Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Mar 20 2007

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