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

1,2

Links

Table of n, a(n) for n=1..40.

Example

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

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

Crossrefs

Cf. A006881.

Sequence in context: A286676 A246379 A303941 * A257731 A257733 A098323

Adjacent sequences: A176882 A176883 A176884 * A176886 A176887 A176888

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 28 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

Status

approved