A098870 - OEIS

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

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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 *)

PadRight[{2, 8, 512, 134, 92, 737, 713}, 100, {371}] (* Harvey P. Dale, Oct 20 2024 *)

CROSSREFS