

A264044


Numbers n such that n and n+4 are consecutive semiprimes.


4



10, 51, 58, 65, 87, 111, 129, 209, 249, 274, 291, 305, 335, 377, 382, 403, 407, 447, 454, 485, 489, 493, 497, 529, 538, 629, 681, 699, 713, 749, 767, 781, 785, 803, 831, 889, 901, 917, 939, 951, 961, 985, 989, 1007, 1037, 1073, 1115, 1191, 1207
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OFFSET

1,1


COMMENTS

Note that a(1)=10=A131109(k=4).
Subsequence of A175648: a(1)=10=A175648(2), a(2)=51=A175648(7), a(3)=58=A175648(8), etc.  Zak Seidov, Dec 20 2017


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000


EXAMPLE

10=A001358(4) and 14=A001358(5).


MAPLE

B:= select(numtheory:bigomega=2, [$1..2000]):
B[select(t >B[t+1]B[t]=4, [$1..nops(B)1])]; # Robert Israel, Dec 21 2017


MATHEMATICA

Select[Partition[Select[Range[1250], PrimeOmega@ # == 2 &], 2, 1], Differences@ # == {4} &][[All, 1]] (* Michael De Vlieger, Dec 20 2017 *)


PROG

(PARI) is(n)=bigomega(n)==2 && bigomega(n+4)==2 && bigomega(n+1)!=2 && bigomega(n+2)!=2 && bigomega(n+3)!=2 \\ Charles R Greathouse IV, Nov 02 2015


CROSSREFS

Cf. A001358, A065516, A123375, A131109, A136196, A175648, A264043.
Sequence in context: A072296 A143558 A106041 * A143855 A124162 A077044
Adjacent sequences: A264041 A264042 A264043 * A264045 A264046 A264047


KEYWORD

nonn


AUTHOR

Zak Seidov, Nov 02 2015


STATUS

approved



