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.

Showing 1-1 of 1 results.

A355702 a(1) = 1, a(2) = 2; for n > 2, a(n) is the smallest positive number that has not yet appeared that has the same number of prime divisors as the sum a(n-2) + a(n-1).

Original entry on oeis.org

1, 2, 3, 5, 8, 7, 4, 11, 6, 13, 17, 12, 19, 23, 18, 29, 31, 16, 37, 41, 20, 43, 27, 28, 9, 47, 24, 53, 10, 30, 36, 42, 44, 14, 15, 59, 21, 32, 61, 22, 67, 71, 45, 50, 25, 52, 26, 63, 73, 40, 79, 33, 48, 54, 66, 72, 68, 56, 70, 60, 75, 81, 84, 76, 64, 88, 90, 34, 78, 80, 35, 38, 83, 39, 46, 49, 51
Offset: 1

Views

Author

Scott R. Shannon, Jul 14 2022

Keywords

Comments

In the first 500000 terms on seventeen occasions the sum of the previous two terms equals the next term, these terms being 3, 5, 8, 11, 100,... ,131072, 262144. It in unknown if there are infinitely many such terms. In the same range there are seventy-three fixed points; see A356017. The sequence is conjectured to be a permutation of the positive integers.

Examples

			a(4) = 5 as a(2) + a(3) = 2 + 3 = 5 which has one prime divisor, and 5 is the smallest unused number that has one prime divisor.
a(6) = 7 as a(4) + a(5) = 5 + 8 = 13 which has one prime divisor, and 7 is the smallest unused number that has one prime divisor.
a(7) = 4 as a(5) + a(6) = 8 + 7 = 15 which has two prime divisors, and 4 is the smallest unused number that has two prime divisors.

Links

Crossrefs

Cf. A356017, A001222, A355647, A355649, A352867.
Showing 1-1 of 1 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.