A048210 T(n,1) + T(n,n), array T given by A048201.

2, 5, 11, 17, 28, 40, 58, 74, 91, 117, 140, 168, 195, 225, 263, 298, 334, 371, 411, 453, 497, 547, 597, 647, 698, 754, 815, 878, 942, 1008, 1074, 1149, 1233, 1316, 1398, 1483, 1570, 1657, 1751, 1843, 1936, 2044, 2152, 2262, 2371

Offset

1,1

Links

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

Formula

a(n) = 2*A004978(n+1) - A004978(n) - 1. - Sean A. Irvine, Jun 05 2021

Prog

(Python)
from itertools import count, accumulate, islice
from collections import deque
def A048210_gen(): # generator of terms
    aset, alist, c = set(), deque(), 0
    for k in count(1):
        if k in aset:
            aset.remove(k)
        else:
            yield (c:=c+k)+k
            aset |= set(k+d for d in accumulate(alist))
            alist.appendleft(k)
A048210_list = list(islice(A048210_gen(), 45)) # Chai Wah Wu, Sep 02 2025

Crossrefs

Cf. A048201, A004978.

Sequence in context: A157421 A274830 A038390 * A153222 A023222 A289250

Adjacent sequences: A048207 A048208 A048209 * A048211 A048212 A048213

Keyword

nonn

Author

Clark Kimberling

Status

approved