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A189475
First differences of A036449, triangular numbers by definition.
3
1, 3, 21, 171, 1485, 435, 16653, 149331, 1342341, 12076155, 990528, 1279200, 263901, 169071, 446985, 133865703, 1180416, 1214185281, 2366400, 25045503, 247275441, 8923200, 19634511, 56525028, 229847520, 739374285, 224497455, 81939201, 24010841091, 1106357280
OFFSET
1,2
LINKS
FORMULA
a(n) = A036449(n+1) - A036449(n). [Corrected by Georg Fischer, Dec 11 2022]
A010054(a(n)) = 1.
PROG
(Haskell) Cf. program in A036449 (simultaneous computation).
(Python)
from itertools import count, islice
from sympy import integer_nthroot
def A189475_gen(): # generator of terms
a = 0
for n in count(1):
if integer_nthroot(((b:=n**2)-a<<3)+1, 2)[1]:
yield b-a
a = b
A189475_list = list(islice(A189475_gen(), 20)) # Chai Wah Wu, Nov 14 2022
CROSSREFS
Subsequence of A000217.
Sequence in context: A220103 A132805 A372459 * A331328 A372089 A206178
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 23 2011
STATUS
approved