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Search: id:A079148
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| A079148 |
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Primes p such that p-1 has at most 2 prime factors, counted with multiplicity; i.e. primes p such that bigomega(p-1) = A001222(p-1) <= 2. |
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+0
12
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| 2, 3, 5, 7, 11, 23, 47, 59, 83, 107, 167, 179, 227, 263, 347, 359, 383, 467, 479, 503, 563, 587, 719, 839, 863, 887, 983, 1019, 1187, 1283, 1307, 1319, 1367, 1439, 1487, 1523, 1619, 1823, 1907, 2027, 2039, 2063, 2099, 2207, 2447, 2459, 2579, 2819, 2879
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Sum of reciprocals ~ 1.477.
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EXAMPLE
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83 is in the sequence because 83-1 = 2*41 has 2 prime factors.
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PROGRAM
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(PARI) s(n) = {sr=0; forprime(x=2, n, if(bigomega(x-1) < 3, print1(x" "); sr+=1.0/x; ); ); print(); print(sr); } \\ Lists primes p<=n such that p-1 has at most 2 prime factors.
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CROSSREFS
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Except for 2 and 3, this is identical to A005385. Cf. A079147, A079149, A079151.
Except for 2, this is identical to A005385.
Sequence in context: A165802 A107798 A119660 this_sequence A107367 A036342 A114421
Adjacent sequences: A079145 A079146 A079147 this_sequence A079149 A079150 A079151
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Dec 27 2002
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