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A122488 Numbers n such that 1+2n+3n^2 is semiprime. 0
1, 3, 4, 5, 6, 8, 9, 10, 11, 15, 20, 21, 22, 29, 30, 33, 35, 36, 40, 42, 45, 47, 48, 50, 54, 57, 59, 60, 64, 66, 69, 72, 75, 76, 77, 78, 80, 81, 82, 84, 86, 89, 95, 96, 100, 102, 108, 110, 111, 112, 113, 116, 123, 125, 130, 131, 132, 134, 136, 143, 146, 147, 148, 152, 153 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

Cf. A086285 (Numbers n such that 1+2n+3n^2 is prime).

EXAMPLE

n=3 is OK because 1+2n+3n^2=34=2*17 (semiprime)

n=4 is OK because 1+2n+3n^2=57=3*19 (semiprime), etc.

MATHEMATICA

Select[Range[160], PrimeOmega[1+2#+3#^2]==2&] (* From Harvey P. Dale, Aug 22 2011 *)

CROSSREFS

Cf. A086285.

Sequence in context: A047207 A039132 A187970 * A039095 A001957 A184484

Adjacent sequences:  A122485 A122486 A122487 * A122489 A122490 A122491

KEYWORD

nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), Oct 20 2006

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Last modified February 14 23:53 EST 2012. Contains 205689 sequences.