A176885 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.

1, 3, 9, 2, 32, 21, 51, 122, 111, 282, 237, 560, 489, 1898, 1794, 6200, 995, 2017, 13428, 19154, 4059, 2166, 8151, 73212, 16341, 58208, 89088, 176186, 32721, 383766, 65483, 530072, 1940958, 131013, 740022, 262083, 1592642, 4781120, 5634480, 524221

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 28 2010

Keywords

• nonn

Examples

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

Crossrefs

Cf. A006881.

Programs

Maple

A176885 := proc(n) c := A006881(n) ; pm := A020639(c) ; pk := A006530(c) ; pm^ numtheory[pi](pk) -pk^numtheory[pi](pm) ; end proc:
seq(A176885(n),n=1..80) ; # R. J. Mathar, May 01 2010

Extensions

a(14) and a(15) corrected and sequence extended by R. J. Mathar, May 01 2010

Definition clarified by N. J. A. Sloane, Feb 16 2019