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A077654 Composite n such that 2n+1 is also composite. 1
4, 10, 12, 16, 22, 24, 25, 27, 28, 32, 34, 38, 40, 42, 45, 46, 49, 52, 55, 57, 58, 60, 62, 64, 66, 70, 72, 76, 77, 80, 82, 84, 85, 87, 88, 91, 92, 93, 94, 100, 102, 104, 106, 108, 110, 112, 115, 117, 118, 121, 122, 123, 124, 126, 129, 130 (list; graph; refs; listen; history; internal format)
OFFSET

0,1

EXAMPLE

Both 16 and 33 = 16*2+1 are composite, so 16 is in this sequence.

PROG

(PARI) isA077654(n) = !(isprime(n)) & !(isprime(2*n+1)); [From Michael Porter (michael_b_porter(AT)yahoo.com), Oct 01 2009]

CROSSREFS

Cf. A005384, A005385, A067812.

Sequence in context: A155475 A023693 A181053 * A095275 A117099 A026180

Adjacent sequences:  A077651 A077652 A077653 * A077655 A077656 A077657

KEYWORD

nonn

AUTHOR

Lior Manor (lior.manor(AT)gmail.com) Nov 13 2002

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Last modified February 15 21:27 EST 2012. Contains 205859 sequences.