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A108215
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4-almost primes equal to the product of two successive semiprimes.
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1
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24, 54, 90, 140, 210, 315, 462, 550, 650, 858, 1122, 1190, 1330, 1482, 1794, 2254, 2499, 2805, 3135, 3306, 3596, 4030, 4485, 5106, 5698, 6314, 6970, 7310, 7482, 7917, 8463, 8742, 8930, 10070, 11766, 12765, 13570, 14042, 14399, 14762, 15006, 15867
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 1..1000
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EXAMPLE
| a(1) = 4*6 = 24 and a(2) = 6*9 = 54 because 4, 6 and 9 are the first three successive semiprimes.
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MATHEMATICA
| Select[Times@@@Partition[Select[Range[200], PrimeOmega[#]==2&], 2, 1], PrimeOmega[#]==4&] (* From Harvey P. Dale, Nov 17 2011 *)
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PROG
| (PARI) sp=4; for(sq=6, 300, if(bigomega(sq)==2, print1(sp*sq, ", "); sp=sq)) (Shepherd)
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CROSSREFS
| Sequence in context: A070197 A190524 A084586 * A038635 A005782 A003756
Adjacent sequences: A108212 A108213 A108214 * A108216 A108217 A108218
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KEYWORD
| easy,nonn
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AUTHOR
| Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Jun 16 2005
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EXTENSIONS
| More terms from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Jun 16 2005
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