A171995 - OEIS

A171995

Twin natural nonprimes with nonprime number of prime factors.

1, 625, 1715, 1925, 2125, 2875, 2975, 3575, 3773, 4165, 4225, 4235, 4625, 5125, 5375, 5425, 5635, 5831, 5875, 5915, 6517, 6625, 7007, 7225, 7315, 7375, 7595, 7625, 7735, 7889, 7975, 8075, 8225, 8281, 8855, 8875, 9025, 9425, 9775, 9875, 10045, 10075

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OFFSET

1,2

COMMENTS

Intersection of A171697 and A167175. - R. J. Mathar, Mar 29 2010

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

a(1)=1(without prime factors), a(2)=625(=5*5*5*5), a(3)=1715(=5*7*7*7).

PROG

(PARI) isA171995(n)=n>0&!isprime(n)&((n%6==1&!isprime(n-2))||(n%6==5&!isprime(n+2)))&!isprime(bigomega(n))

CROSSREFS

Cf. A167175, A171697.

Sequence in context: A186483 A043352 A223183 * A307481 A262798 A250431

Adjacent sequences: A171992 A171993 A171994 * A171996 A171997 A171998

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Jan 21 2010

EXTENSIONS

Edited and extended by Charles R Greathouse IV, Mar 29 2010

STATUS

approved