Search ProblemsRSS Feed
projecteuler.net

Sum of digits sequence

Problem 551 Published on Saturday, 12th March 2016, 04:00 pm; Solved by 337;
Difficulty rating: 50%

Let a0, a1, a2, ... be an integer sequence defined by:

  • a0 = 1;
  • for n ≥ 1, an is the sum of the digits of all preceding terms.

The sequence starts with 1, 1, 2, 4, 8, 16, 23, 28, 38, 49, ...
You are given a106 = 31054319.

Find a1015.