A155104 Numbers appearing in the fourth column of A155103.

1, 5, 45, 765, 25245, 1640925, 211679325, 54401586525, 27908013887325, 28605714234508125, 58613108466507148125, 240137905387279785868125, 1967449858837983285617548125, 32236665937060356134843526028125

Offset

1,2

Links

Table of n, a(n) for n=1..14.

Formula

a(n) = prod(k=2..n) (1+2^k), n>1. - Mats Granvik, Simone Severini, Dec 04 2010

a(n) = A028362(n+1)/3. - Vladimir Reshetnikov, Sep 16 2016

Example

a(1)=1, a(2)=1*5, a(3)=1*5*9, a(4)=1*5*9*17, a(5)=1*5*9*17*33, a(6)=1*5*9*17*33*65 and so on. See A000051 for continuation.

Mathematica

Table[QPochhammer[-4, 2, n - 1], {n, 14}] (* Arkadiusz Wesolowski, Oct 29 2012 *)

Crossrefs

Cf. A000051, A155105.

Sequence in context: A132688 A295227 A167812 * A243951 A290941 A211051

Adjacent sequences: A155101 A155102 A155103 * A155105 A155106 A155107

Keyword

nonn

Author

Mats Granvik, Jan 20 2009

Extensions

More terms from Mats Granvik, Dec 05 2010

Status

approved