A165144 Number of semiprimes between two primes squared.

1, 5, 7, 22, 15, 33, 23, 49, 88, 35, 114, 79, 48, 100, 148, 189, 57, 201, 139, 78, 230, 158, 269, 370, 192, 102, 215, 112, 211, 803, 259, 390, 150, 666, 147, 430, 471, 317, 485, 506, 152, 869, 168, 364, 184, 1144, 1213, 404, 206, 433, 613, 217, 1134, 702, 720, 712

Offset

1,2

Links

Table of n, a(n) for n=1..56.

Formula

a(n) = A217019(n) - 1. - Flávio V. Fernandes, Nov 19 2020

Maple

A165144 := proc(n) a := 0 ; for k from ithprime(n)^2+1 to ithprime(n+1)^2-1 do if numtheory[bigomega](k) = 2 then a := a+1 ; fi ; end do ; a ; end proc: seq(A165144(n), n=1..80) ; # R. J. Mathar, Jan 30 2010

Mathematica

Table[Count[Range[Prime[p]^2+1, Prime[p+1]^2-1], _?(PrimeOmega[#]==2&)], {p, 60}] (* Harvey P. Dale, Oct 05 2024 *)

Crossrefs

Cf. A001248 (primes squared), A001358 (semiprimes), A217019.

Sequence in context: A030735 A303189 A162462 * A084164 A036498 A350193

Adjacent sequences: A165141 A165142 A165143 * A165145 A165146 A165147

Keyword

nonn

Author

Giovanni Teofilatto, Sep 05 2009

Extensions

a(7) corrected and terms beyond a(7) added by R. J. Mathar, Jan 30 2010

Status

approved