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 A265650 Removing the first occurrence of 1, 2, 3, ... reproduces the sequence itself. Each run of consecutive removed terms is separated from the next one by a term a(k) <= a(k-1) such that floor(sqrt(a(k))) equals the length of the run. 4
 1, 1, 2, 1, 3, 2, 4, 1, 5, 3, 6, 2, 7, 8, 4, 9, 1, 10, 11, 5, 12, 3, 13, 14, 6, 15, 2, 16, 17, 7, 18, 19, 8, 20, 21, 4, 22, 23, 24, 9, 25, 1, 26, 27, 28, 10, 29, 30, 31, 11, 32, 33, 5, 34, 35, 36, 12, 37, 3, 38, 39, 40, 13, 41, 42, 43, 14, 44, 45, 6, 46, 47, 48, 15, 49, 2, 50, 51, 52, 53, 16, 54, 55, 56, 57, 17, 58, 59, 7, 60, 61, 62, 63, 18, 64, 65, 66 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS A fractal sequence : If one deletes the first occurrence of 1, 2, 3, ... the original sequence is reproduced. Subsequent runs of consecutive terms which are these first occurrences are separated by a term whose square root yields the length of the preceding run (when rounded down). Motivated by Project Euler problem 535, see LINKS. LINKS Martin Møller Skarbiniks Pedersen, Table of n, a(n) for n = 1..1000 Project Euler, Problem 535 Clark Kimberling, Interspersions and Fractal Sequences Associated with Fractions c^j/d^k, Journal of Integer Sequences, Issue 5, Volume 10 (2007), Article 07.5.1 FORMULA The sequence contains marked numbers and non-marked numbers. The marked numbers are consecutive starting with a(1)=1. Immediately preceding each non-marked number in a(n), there are exactly floor(sqrt(a(n)) [= A000196(a(n))] adjacent marked numbers. EXAMPLE The runs of first occurrences of the positive integers are {1}, {2}, {3}, {4}, {5}, {6}, {7, 8}, {9}, {10, 11}, ... each separated from the next one by, respectively, 1, 1, 2, 1, 3, 2, 4, 1, 5, ... where 4 and 5 follow the groups {7, 8} and {10, 11} of length 2 = sqrt(4) = floor(sqrt(5)). - M. F. Hasler, Dec 13 2015 PROG (C) #include #include #define SIZE 1000 unsigned int numbers[SIZE]; int main() {   unsigned int pointer=0, next=1, circle_count=1, next_circle_number=2, sqrt_non_circle=1;   numbers[0]=1; printf("1");   while (next

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Last modified August 19 13:00 EDT 2017. Contains 290807 sequences.