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 A088701 Smallest semiprime such that n primes will follow until the next semiprime. 2
 9, 4, 10, 95, 818, 2681, 16053, 35981, 797542, 1069541, 340894, 6974465, 3586843, 2070050198, 5238280946, 14499777101, 2601693504238, 7472089131123 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Is this sequence infinite? - David A. Corneth, Aug 17 2018 LINKS FORMULA A088700(a(n)) = n and A088700(k) <> n for 1 <= k < a(n). MATHEMATICA om = Array[PrimeOmega, 1100000]; sp = Flatten@ Position[om, 2]; Table[ sp[[ SelectFirst[ Range[Length[sp] - 1], Count[Take[om, {sp[[#]], sp[[# + 1]]}], x_ /; x == 1] == j &, 0]]], {j, 0, 10}] (* Giovanni Resta, Aug 16 2018 *) PROG (Perl) use ntheory ":all"; my(\$l, \$nextn, @C)=(4, 0); forcomposites {   if (is_semiprime(\$_)) {     my \$c = prime_count(\$l+1, \$_-1);     if (!defined \$C[\$c]) {       \$C[\$c] = \$l;       while (defined \$C[\$nextn]) { print "\$nextn \$C[\$nextn]\n"; \$nextn++; }     }     \$l = \$_;   } } 5, 1e7;  # Dana Jacobsen, Aug 16 2018 CROSSREFS Cf. A214520 (primes that are the only prime between consecutive semiprimes). Sequence in context: A154201 A253203 A255642 * A153698 A168203 A248310 Adjacent sequences:  A088698 A088699 A088700 * A088702 A088703 A088704 KEYWORD nonn,more AUTHOR Reinhard Zumkeller, Oct 08 2003 EXTENSIONS a(11)-a(15) from Donovan Johnson, Mar 14 2010 a(16) from Giovanni Resta, Aug 17 2018 a(17) from Giovanni Resta, Aug 18 2018 STATUS approved

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Last modified August 22 11:34 EDT 2019. Contains 326176 sequences. (Running on oeis4.)