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A175588 a(1) = 4; a(n) = smallest semiprime > a(n-1) such that a(n) - a(n-1) is semiprime. 2
4, 10, 14, 35, 39, 49, 55, 65, 69, 91, 95, 121, 142, 146, 155, 159, 169, 178, 187, 201, 205, 209, 213, 217, 221, 235, 249, 253, 259, 265, 274, 278, 287, 291, 295, 299, 303, 309, 319, 323, 327, 341, 355, 361, 365, 371, 377, 381, 391, 395, 417, 427, 437, 446 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Subsequence of semiprimes with semiprime gaps.
LINKS
MATHEMATICA
Nest[Append[#, Block[{k = #[[-1]] + 1}, While[! AllTrue[{k, k - #[[-1]]}, PrimeOmega[#] == 2 &], k++]; k]] &, {4}, 53] (* Michael De Vlieger, Dec 23 2019 *)
PROG
(PARI) (nxt_A175588(t)=for(d=4, oo, bigomega(d)==2&&bigomega(t+d)==2&&return(t+d))); vector(99, i, t=nxt_A175588(if(i>1, t))) \\ M. F. Hasler, Dec 22 2019
CROSSREFS
Cf. A175587 (subsequence of semiprimes with prime gaps), A001358 (semiprimes).
Sequence in context: A162521 A125302 A365679 * A239788 A136862 A191635
KEYWORD
nonn
AUTHOR
Zak Seidov, Jul 17 2010
STATUS
approved

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Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)