A098870 Sum of the cubes of the digits of the previous term, starting with 2.

2, 8, 512, 134, 92, 737, 713, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371, 371

Offset

1,1

Comments

A student of mine (Dennis Vadner) noted this sequence when working with the sequence formed by summing the squares of the digits of the previous term for a class assignment. Upon investigating various initial terms, it was noted that there appeared to be a limited number of end behaviors.

Links

Table of n, a(n) for n=1..53.

Erich Friedman, What's Special About This Number?, 371.

Index entries for linear recurrences with constant coefficients, signature (1).

Formula

G.f.: x*(342*x^7 + 24*x^6 - 645*x^5 + 42*x^4 + 378*x^3 - 504*x^2 - 6*x - 2) / (x - 1). - Jinyuan Wang, Mar 18 2020

Example

Since a(5) = 92, a(6) is therefore 9^3 + 2^3 = 729 + 8 = 737.

Mathematica

FixedPointList[Plus@@(IntegerDigits[#]^3) &, 2] (* Alonso del Arte, Mar 18 2020 *)

Crossrefs

Cf. A000216.

Sequence in context: A003301 A000890 A033542 * A221065 A023365 A262826

Adjacent sequences: A098867 A098868 A098869 * A098871 A098872 A098873

Keyword

nonn,base

Author

Gary Nagel (gary.nagel(AT)sendit.nodak.edu), Oct 12 2004

Extensions

Offset changed to 1 by and more terms from Jinyuan Wang, Mar 18 2020

Status

approved