This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

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