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A358417
Indices of the triangular numbers in A189475.
0
1, 2, 6, 18, 54, 29, 182, 546, 1638, 4914, 1407, 1599, 726, 581, 945, 16362, 1536, 49278, 2175, 7077, 22238, 4224, 6266, 10632, 21440, 38454, 21189, 12801, 219138, 47039, 37494, 119837, 19158, 760898, 182840, 7649, 536847, 75405, 544775, 160520, 365439, 307943
OFFSET
1,2
FORMULA
A000217(a(n)) = A189475(n).
PROG
(Python)
from itertools import islice, count
from sympy import integer_nthroot
def A358417_gen(): # generator of terms
a = 0
for n in count(1):
c, d = integer_nthroot(((b:=n**2)-a<<3)+1, 2)
if d:
yield c-1>>1
a = b
A358417_list = list(islice(A358417_gen(), 44))
CROSSREFS
KEYWORD
nonn
AUTHOR
Chai Wah Wu, Nov 14 2022
STATUS
approved