A247982 Number of inequivalent expressions involving n operands, ignoring sign.

1, 5, 47, 733, 15907, 443825, 15129599, 609432421, 28322451979, 1491650309705, 87799033276583, 5711697248522077, 406948643125302163, 31515118552199419745, 2635823964117955940111, 236779241276954626064149, 22736883802469421935493211

Offset

1,2

Comments

Similar to A140606, but for example, (a-b)/(c-d) and (b-a)/(c-d) are also regarded as the same.

Links

Muniru A Asiru, Table of n, a(n) for n = 1..100

Azuma Seiichi, Expressions with n variables

Formula

a(n) = A182173(n)/2. - Zhujun Zhang, Aug 11 2018

Crossrefs

Cf. A140606, A182173.

Sequence in context: A086555 A246040 A183773 * A222078 A061572 A140422

Adjacent sequences: A247979 A247980 A247981 * A247983 A247984 A247985

Keyword

nonn,more

Author

Azuma Seiichi, Sep 28 2014

Extensions

a(7)-a(17) from Muniru A Asiru, Aug 13 2018

Status

approved