A369899 a(1) = 1, a(2) = 2; for n > 2, a(n) is the smallest unused positive number that is a substring of the sum of all previous terms.
1, 2, 3, 6, 12, 4, 8, 36, 7, 9, 88, 17, 19, 21, 23, 5, 26, 28, 15, 30, 60, 20, 40, 48, 52, 58, 38, 67, 43, 78, 64, 92, 10, 103, 11, 14, 115, 27, 13, 31, 34, 37, 41, 45, 50, 51, 16, 18, 63, 69, 68, 83, 91, 201, 22, 33, 66, 32, 236, 260, 86, 29, 75, 305, 35, 39, 42, 47, 351, 386, 25, 80, 360, 72
Offset: 1
Examples
a(6) = 4 as the sum of all previous terms is 1 + 2 + 3 + 6 + 12 = 24, and 4 is the smallest unused number that is a substring of "24".
Links
- Scott R. Shannon, Table of n, a(n) for n = 1..10000
- Scott R. Shannon, Image of the first 50000 terms.
Programs
-
Python
from itertools import islice def agen(): # generator of terms s, mink, aset = 3, 3, {1, 2} yield from [1, 2] while True: an, ss = mink, str(s) while an in aset or not str(an) in ss: an += 1 aset.add(an); s += an; yield an while mink in aset: mink += 1 print(list(islice(agen(), 74))) # Michael S. Branicky, Feb 08 2024
Comments