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A143804 Triangle read by rows, thrice the Connell numbers (A001614) - 2. 2
1, 4, 10, 13, 19, 25, 28, 34, 40, 46, 49, 55, 61, 67, 73, 76, 82, 88, 94, 100, 106, 109, 115, 121, 127, 133, 139, 145, 148, 154, 160, 166, 172, 178, 184, 190, 193, 199, 205, 211, 217, 223, 229, 235, 241, 244, 250, 256, 262, 268, 274, 280, 286, 292, 298 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Right border of the triangle = A100536: (1, 10, 25, 46, 73,...).
Left border = A056107: (1, 4, 13, 28, 49,...)
Row sums = A005915: (1, 14, 57, 148, 305,...).
n-th row = (right border then going to the left): (n-th term of A100536 followed by (n-1) operations of (-6), (-6), (-6),... As a Connell-like triangle, odd row terms are in the subset 6n-5; even row terms are in the set 6n-2.
First few rows of the triangle = 1;
4, 10;
13, 19, 25;
28, 34, 40, 46;
49, 55, 61, 67, 73;
76, 82, 88, 94, 100, 106;
...
Examples: a(5) = 19 = 3*A001614 - 2 = 3*(7) - 2.
Row 3 = (13, 19, 25) beginning with A100536(3) = 25 at the right then following the trajectory (-6), (-6).
Using the modular rules, the triangle begins (1; 4, 10; 13, 19, 25;...) since 1 == 6n-5, while 4 is the next higher term in the set 6n-2, then 10 also in the set 6n-2, being an even row.
LINKS
FORMULA
a(n) = 3*A001614(n) - 2
PROG
(Python)
from math import isqrt
def A143804(n): return 3*((m:=n<<1)-(k:=isqrt(m))-int(m>=k*(k+1)+1))-2 # Chai Wah Wu, Aug 01 2022
CROSSREFS
Sequence in context: A087444 A310357 A310358 * A342742 A152843 A139121
KEYWORD
nonn,tabl
AUTHOR
Gary W. Adamson, Sep 01 2008
STATUS
approved

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Last modified March 19 02:51 EDT 2024. Contains 370952 sequences. (Running on oeis4.)