A335830 Decimal expansion of the sum of the reciprocals of the multiply-perfect numbers.

1, 2, 1, 4, 4, 0, 7, 6, 0, 8, 5, 9, 1, 4, 2, 7, 1, 9, 2, 9, 0, 6, 3, 8, 6, 3, 7, 3, 9, 0, 8, 2, 1, 8, 5, 6, 7, 8, 2, 2, 2, 7, 0, 6, 3, 1, 2, 8, 3, 4, 0, 8, 9, 0, 1, 1, 8, 6, 5, 6, 3, 9, 6, 2, 4, 2, 3, 9, 9, 3, 3, 9, 0, 1, 7, 8, 4, 4, 8, 4, 1, 6, 8, 0, 7, 8, 8, 8, 0, 0, 0, 8, 8, 8, 8, 6, 1, 9, 2, 9

Offset

1,2

Comments

The first 18 terms were calculated by Bayless and Kinlaw (2015).

Links

Table of n, a(n) for n=1..100.

Jonathan Bayless and Paul Kinlaw, On repeated values of sigma and multiperfect numbers, Journal of Combinatorics and Number Theory, Vol. 7, No. 3 (2015), pp. 177-189.

Formula

Equals Sum_{k>=1} 1/A007691(k).

Example

1.21440760859142719...

Mathematica

multiPerfects = Cases[Import["https://oeis.org/A007691/b007691.txt", "Table"], {_, _}][[;; , 2]]; RealDigits[Total[1/multiPerfects], 10, 18][[1]]

Crossrefs

Cf. A007691, A335118.

Sequence in context: A009477 A324658 A105568 * A004175 A136756 A214670

Adjacent sequences: A335827 A335828 A335829 * A335831 A335832 A335833

Keyword

nonn,cons

Author

Amiram Eldar, Jun 25 2020

Extensions

More terms (computed using the b-file at A007691) from Jon E. Schoenfield, Jan 25 2021

Status

approved