cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A333000 Sum of integers (with multiplicity) encountered on all possible paths from n to 1 when iterating with nondeterministic map k -> k- k/p, where p is any prime factor of k.

Original entry on oeis.org

1, 3, 6, 7, 12, 25, 39, 15, 43, 47, 69, 76, 115, 185, 198, 31, 48, 209, 304, 138, 604, 317, 432, 203, 213, 500, 344, 640, 901, 899, 1271, 63, 1777, 179, 2274, 736, 1069, 1572, 1860, 361, 525, 3156, 4360, 1074, 2580, 2150, 2808, 506, 4528, 924, 1042, 1630, 2266, 1836, 2878, 1930, 5004, 4165, 5522, 3026, 4307, 6343, 7638, 127, 6801
Offset: 1

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Author

Antti Karttunen, Apr 06 2020

Keywords

Examples

			a(12): we have three alternative paths: {12, 8, 4, 2, 1}, {12, 6, 4, 2, 1} or {12, 6, 3, 2, 1}, therefore a(12) = (12+8+4+2+1) + (12+6+4+2+1) + (12+6+3+2+1) = 27+25+24 = 76
For n=15 we have five alternative paths from 15 to 1 (illustrated below): therefore a(15) = (15+10+5+4+2+1) + (15+10+8+4+2+1) + (15+12+8+4+2+1) + (15+12+6+4+2+1) + (15+12+6+3+2+1) = 37+40+42+40+39 = 198.
        15
       / \
      /   \
    10     12
    / \   / \
   /   \ /   \
  5     8     6
   \__  |  __/|
      \_|_/   |
        4     3
         \   /
          \ /
           2
           |
           1.
		

Crossrefs

Programs

  • PARI
    up_to = 20000;
    A333000list(up_to) = { my(u=vector(up_to), v=vector(up_to)); u[1] = v[1] = 1; for(n=2,up_to, u[n] = vecsum(apply(p -> u[n-n/p], factor(n)[, 1]~)); v[n] = (u[n]*n)+vecsum(apply(p -> v[n-n/p], factor(n)[, 1]~))); (v); };
    v333000 = A333000list(up_to);
    A333000(n) = v333000[n];

Formula

a(n) = n*A333123(n) + Sum_{p prime and dividing n} a(n - n/p).
For all n, a(n) >= A332904(n).