OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..100
Edinah K. Ghang, Doron Zeilberger, Zeroless Arithmetic: Representing Integers ONLY using ONE, arXiv:1303.0885v1 [math.CO], 2013
Shalosh B. Ekhad, Everything About Formulas Representing Integers Using Additions and Multiplication for integers from 1 to 8000
Wikipedia, Postfix notation
EXAMPLE
a(1) = 1: 1.
a(2) = 3: 11+.
a(3) = 10: 111++, 11+1+.
a(4) = 42: 1111+++, 111+1++, 11+11++, 111++1+, 11+1+1+, 11+11+*.
a(5) = 144: 11111++++, 1111+1+++, 111+11+++, 1111++1++, 111+1+1++, 111+11+*+, 11+111+++, 11+11+1++, 111++11++, 11+1+11++, 1111+++1+, 111+1++1+, 11+11++1+, 111++1+1+, 11+1+1+1+, 11+11+*1+.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 07 2013
STATUS
approved