A345984 Partial sums of A011772.

1, 4, 6, 13, 17, 20, 26, 41, 49, 53, 63, 71, 83, 90, 95, 126, 142, 150, 168, 183, 189, 200, 222, 237, 261, 273, 299, 306, 334, 349, 379, 442, 453, 469, 483, 491, 527, 546, 558, 573, 613, 633, 675, 707, 716, 739, 785, 817, 865, 889, 906, 945, 997, 1024, 1034, 1082, 1100, 1128, 1186, 1201, 1261

Offset

1,2

Comments

How fast is this growing?

Links

N. J. A. Sloane, Table of n, a(n) for n = 1..16383

Mathematica

Accumulate[(Sqrt[1+8#]-1)/2&/@Flatten[With[{r=Accumulate[ Range[ 300]]}, Table[ Select[ r, Divisible[#, n]&, 1], {n, 80}]]]] (* Harvey P. Dale, Sep 19 2021 *)

Prog

(Python 3.8+)
from itertools import combinations, count, islice
from math import prod
from sympy import factorint
from sympy.ntheory.modular import crt
def A345984_gen(): # generator of terms
    c = 1
    for n in count(4, 2):
        yield c
        plist = tuple(p**q for p, q in factorint(n).items())
        c += n-1 if len(plist) == 1 else int(min(min(crt((m, n//m), (0, -1))[0], crt((n//m, m), (0, -1))[0]) for m in (prod(d) for l in range(1, len(plist)//2+1) for d in combinations(plist, l))))
A345984_list = list(islice(A345984_gen(), 25)) # Chai Wah Wu, Jun 01 2022

Crossrefs

Cf. A011772, A344005, A345983.

Sequence in context: A249715 A249440 A063186 * A191198 A191137 A247284

Adjacent sequences: A345981 A345982 A345983 * A345985 A345986 A345987

Keyword

nonn

Author

N. J. A. Sloane, Jul 09 2021

Status

approved