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

1,4

Links

Table of n, a(n) for n=1..24.

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

a(n) = A054973(A002110(n)). - Ray Chandler, Dec 28 2008

Example

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.

Crossrefs

Cf. A000203, A002110, A153076, A153077.

Sequence in context: A245635 A111861 A004543 * A245565 A233468 A076200

Adjacent sequences: A153075 A153076 A153077 * A153079 A153080 A153081

Keyword

nonn,more

Author

Donovan Johnson, Dec 19 2008

Extensions

a(12)-a(21) from Ray Chandler, Dec 28 2008

a(22)-a(24) from Max Alekseyev, Jan 27 2012

Status

approved