

A349094


a(n) = 2^(n1)  tau(n) where tau(n) is the number of divisors of n.


0



0, 0, 2, 5, 14, 28, 62, 124, 253, 508, 1022, 2042, 4094, 8188, 16380, 32763, 65534, 131066, 262142, 524282, 1048572, 2097148, 4194302, 8388600, 16777213, 33554428, 67108860, 134217722, 268435454, 536870904, 1073741822, 2147483642, 4294967292, 8589934588
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OFFSET

1,3


COMMENTS

Considering that there are 2^(n1) compositions (ordered partitions) of n, then tau(n) represents the number of compositions whose terms are all equal. Subtracting tau(n) from 2^(n1) gives the number of compositions whose terms are not all equal.


LINKS



FORMULA



EXAMPLE

For n = 6, a(6) = 28 because from all the possible compositions (32 in this case) there are four whose terms are equal: 6, 3+3, 2+2+2, 1+1+1+1+1+1.


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



STATUS

approved



