A048204 a(n) = T(n+1,n), array T given by A048201.

2, 6, 11, 19, 29, 43, 58, 74, 95, 117, 142, 168, 196, 229, 263, 298, 334, 372, 412, 454, 500, 548, 597, 647, 700, 757, 817, 879, 943, 1008, 1078, 1155, 1235, 1316, 1399, 1484, 1570, 1660, 1751, 1843, 1943, 2047, 2154, 2262, 2378, 2497, 2621, 2748, 2880, 3013

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• changed

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004978, A048201.

Programs

Python

from itertools import count, accumulate, islice
from collections import deque
def A048204_gen(): # generator of terms
    aset, alist, c = {1}, deque([1]), 0
    for k in count(2):
        if k in aset:
            aset.remove(k)
        else:
            yield (c:=c+k)
            aset |= set(k+d for d in accumulate(alist))
            alist.appendleft(k)
A048204_list = list(islice(A048204_gen(),50)) # Chai Wah Wu, Sep 01 2025

Formula

a(n) = A004978(n+2) - 2. - Sean A. Irvine, Jun 05 2021