A078443 Numbers which are both interprime and semiprime.

4, 6, 9, 15, 21, 26, 34, 39, 69, 86, 93, 111, 129, 134, 205, 217, 254, 274, 309, 334, 381, 386, 393, 446, 453, 473, 489, 501, 515, 566, 667, 687, 723, 771, 803, 879, 933, 939, 974, 1003, 1011, 1126, 1167, 1207, 1226, 1234, 1243, 1286, 1294, 1299, 1313, 1465

Offset

1,1

Comments

Ratio of the number of odd terms to the number of even terms increases with increasing n. - Zak Seidov, May 22 2015

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

a[8]=39 because 39=(37+41)/2 and 39=3*13

Mathematica

Select[Mean/@Partition[Prime[Range[250]], 2, 1], PrimeOmega[#]==2&] (* Harvey P. Dale, Oct 08 2013 *)

Prog

(PARI) lista(nn) = {prevp = 2; forprime (p=3, nn, n = p + prevp; if (n % 2 == 0, if (bigomega(n/2) == 2, print1(n/2, ", "); ); ); prevp = p; ); } \\ Michel Marcus, Jun 09 2013

Crossrefs

Intersection of A001358 and A024675. - Zak Seidov, May 22 2015

Sequence in context: A086697 A287568 A251728 * A085751 A263106 A344468

Adjacent sequences: A078440 A078441 A078442 * A078444 A078445 A078446

Keyword

nonn

Author

Lior Manor, Dec 31 2002

Status

approved