A176579 - OEIS

This site is supported by donations to The OEIS Foundation.

A176579

Primes p that exactly one of 2p-1, 2p+1 is semiprime.

5, 7, 11, 13, 19, 29, 59, 67, 73, 79, 89, 103, 127, 149, 163, 167, 181, 191, 227, 241, 251, 257, 263, 269, 271, 277, 283, 311, 347, 353, 359, 373, 383, 389, 397, 401, 409, 433, 439, 449, 457, 467, 479, 487, 503, 523, 541, 557, 571, 599, 601, 613, 643, 647, 659, 677, 691, 709, 719, 733, 739, 751, 757, 769, 811, 827, 839, 853 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,1`
	LINKS	`Table of n, a(n) for n=1..68.`
	EXAMPLE	`a(1)=5 because 25-1=9=semiprime and 25+1=11=non-semiprime.`
	MAPLE	`Contribution from R. J. Mathar, Dec 12 2010: (Start)` `isA001358 := proc(n) is(numtheory[bigomega](n) = 2) ; end proc:` `for n from 1 to 120 do p := ithprime(n) ; if isA001358(2p-1) <> isA001358(2p+1) then printf("%d, ", p); end if; end do: (End)`
	CROSSREFS	`Cf. A001358.` `Sequence in context: A088664 A023219 A045438 * A154275 A167460 A045439` `Adjacent sequences: A176576 A176577 A176578 * A176580 A176581 A176582`
	KEYWORD	`nonn`
	AUTHOR	`Juri-Stepan Gerasimov, Apr 20 2010`
	STATUS	`approved`

Content is available under The OEIS End-User License Agreement .

Last modified May 22 15:33 EDT 2013. Contains 225552 sequences.