Consider a decimal number of k>=2 digits z = d_(k)*10^(k-1) + d_(k-1)*10^(k-2) + ... + d_(2)*10 + d_(1) and the sum y = Sum_{x=2..k} {Sum_{j=1..k-x}{d_(j+x-1)*10^(j-1)} - Sum_{j=1..x-1}{d_(j)*10^(j-1)}}. Sequence lists the numbers for which y = tau(z), where tau(z) is the number of divisors of z.
A248904
Consider a decimal number of k>=2 digits z = d_(k)*10^(k-1) + d_(k-1)*10^(k-2) + ... + d_(2)*10 + d_(1) and the sum y = Sum_{x=2..k} {Sum_{j=1..k-x}{d_(j+x-1)*10^(j-1)} - Sum_{j=1..x-1}{d_(j)*10^(j-1)}}. Sequence lists the numbers for which y = tau(z), where tau(z) is the number of divisors of z.
Terms
- a(0) =31a(1) =51a(2) =53a(3) =62a(4) =95a(5) =97a(6) =209a(7) =318a(8) =429a(9) =443a(10) =553a(11) =886a(12) =887a(13) =2165a(14) =2217a(15) =4387a(16) =4439a(17) =5498a(18) =5553a(19) =6714a(20) =7775a(21) =8932a(22) =10548a(23) =56105a(24) =56107a(25) =78292a(26) =78320a(27) =78324a(28) =78328a(29) =88887
External references
- oeis: A248904