A153078 Number of values of m such that sigma(m) = A002110(n) where A002110(n) is the product of the first n primes.
0, 1, 1, 2, 2, 5, 2, 4, 5, 3, 7, 5, 10, 2, 8, 4, 5, 6, 11, 32, 42, 68, 24, 87
Offset: 1
Examples
a(10) = 3 because 2388809736, 3450503048 and 3696967556 are the only numbers with a sigma value = A002110(10). A002110(10) = 6469693230 = 2*3*5*7*11*13*17*19*23*29.
Links
- Max A. Alekseyev, Computing the Inverses, their Power Sums, and Extrema for Euler's Totient and Other Multiplicative Functions. Journal of Integer Sequences, Vol. 19 (2016), Article 16.5.2.
Formula
Extensions
a(12)-a(21) from Ray Chandler, Dec 28 2008
a(22)-a(24) from Max Alekseyev, Jan 27 2012