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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 9 03:27 EST 2019. Contains 329872 sequences. (Running on oeis4.)