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A074851 Numbers n such that n and n+1 have 2 distinct prime factors. 4
14, 20, 21, 33, 34, 35, 38, 39, 44, 45, 50, 51, 54, 55, 56, 57, 62, 68, 74, 75, 76, 85, 86, 87, 91, 92, 93, 94, 95, 98, 99, 111, 115, 116, 117, 118, 122, 123, 133, 134, 135, 141, 142, 143, 144, 145, 146, 147, 152, 158, 159, 160, 161, 171, 175, 176, 177, 183, 184 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

20=2^2*5 21=3*7 hence 20 is in the sequence

FORMULA

a(n) seems to be asymptotic to c*n*log(n)^2 with c=0.13...

CROSSREFS

Cf. A006549.

Sequence in context: A144080 A006576 A083247 * A193672 A087678 A144585

Adjacent sequences:  A074848 A074849 A074850 * A074852 A074853 A074854

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre (benoit7848c(AT)orange.fr), Sep 10 2002

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Last modified February 15 21:56 EST 2012. Contains 205860 sequences.