The Birthday Of Anwesha Biswas TithiNumber Theory Level 3
Find a decimal number which can be represented with 1's only and no 0's in binary, and takes 4 bits in binary. In other words, if you convert that decimal number into binary, it cannot be like 10101 which does contain 0's. It should only contain a certain number of 1's.
Submit your answer as the sum of digits of the binary-coded decimal of that decimal number.
For binary-coded decimal, read the wiki Binary-Coded Decimal.