A231968 Squarefree numbers (A005117) of the form p*q*r*s with prime factors p, q, r, s with q = 2*p + 1, r = 2*q + 1 and s = 2*r + 1.

2530, 59455, 4112125651, 66487065301, 1069364586601, 4313828719351, 146264252084551, 252626415665851, 3398860950259501, 10045301361318901, 110736954977078251

Offset

1,1

Links

Table of n, a(n) for n=1..11.

Example

4112125651 = 89*179*359*719; 179 = 2*89 + 1; 359 = 2*179 + 1, 719 = 2*359 + 1.

Crossrefs

Cf. A005117, A000040, A231967, A231969, A231966.

Sequence in context: A268332 A369521 A203440 * A172142 A206596 A334932

Adjacent sequences: A231965 A231966 A231967 * A231969 A231970 A231971

Keyword

nonn

Author

Jaroslav Krizek, Nov 18 2013

Status

approved