A176888 - OEIS

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A176888

Unsafe primes minus 1.

0

1, 2, 12, 16, 18, 28, 30, 36, 40, 42, 52, 60, 66, 70, 72, 78, 88, 96, 100, 102, 108, 112, 126, 130, 136, 138, 148, 150, 156, 162, 172, 180, 190, 192, 196, 198, 210, 222, 228, 232, 238, 240, 250, 256, 268, 270, 276, 280, 282, 292, 306, 310, 312, 316, 330, 336

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OFFSET

1,2

COMMENTS

Non-semiprimes k such that k+1 is a prime.

LINKS

Table of n, a(n) for n=1..56.

FORMULA

a(n)=A059456(n)-1.

MATHEMATICA

Select[Prime[Range[70]]-1, PrimeOmega[#]!=2&] (* Harvey P. Dale, Jan 14 2015 *)

CROSSREFS

Sequence in context: A102975 A120300 A089021 * A114974 A298001 A071566

Adjacent sequences: A176885 A176886 A176887 * A176889 A176890 A176891

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Apr 28 2010

EXTENSIONS

Entries checked by R. J. Mathar, May 06 2010

STATUS

approved