A176885 - OEIS

%I #13 Feb 18 2019 04:10:59

%S 1,3,9,2,32,21,51,122,111,282,237,560,489,1898,1794,6200,995,2017,

%T 13428,19154,4059,2166,8151,73212,16341,58208,89088,176186,32721,

%U 383766,65483,530072,1940958,131013,740022,262083,1592642,4781120,5634480,524221

%N Let p*q = A006881(n) be the n-th number that is the product of two distinct primes, with p = prime(i), q=prime(j); a(n) = p^j - q^i.

%e For n=3, A006881(3) = 14 = 2*7, p=2, i=1, q=7, j=4; a(n) = 2^4-7^1 = 9.

%p A176885 := proc(n) c := A006881(n) ; pm := A020639(c) ; pk := A006530(c) ; pm^ numtheory[pi](pk) -pk^numtheory[pi](pm) ; end proc:

%p seq(A176885(n),n=1..80) ; # _R. J. Mathar_, May 01 2010

%Y Cf. A006881.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Apr 28 2010

%E a(14) and a(15) corrected and sequence extended by _R. J. Mathar_, May 01 2010

%E Definition clarified by _N. J. A. Sloane_, Feb 16 2019