A081972 Consider the geometric progression 1,1/2,1/4,1/8,1/16,1/32,1/64,... Group the terms such that the n-th group contains n terms like this (1/1),(1/2,1/4),(1/8,1/16,1,32),(1/64,1/128,1/256,1/512),... a(n) = floor[1/s(n)] where s(n) is the sum of the members of the n-th group.

1, 1, 4, 34, 528, 16644, 1056832, 134744072, 34426978560, 17609382707216, 18023198899569664, 36902497546234101792, 151134176447977081540608, 1238015601761073699807559744, 20283028592561355523908308058112

Offset

1,3

Links

Table of n, a(n) for n=1..15.

Formula

a(n) = floor((2^(n*(n+1)/2 - 1))/(2^n-1)).

Crossrefs

Sequence in context: A198908 A207864 A222077 * A158961 A134354 A333981

Adjacent sequences: A081969 A081970 A081971 * A081973 A081974 A081975

Keyword

nonn

Author

Amarnath Murthy, Apr 03 2003

Extensions

Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 08 2003

Status

approved