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A083487 Triangle read by rows: T(r,c) = 2*r*c + l + c (1 <= c <= l). 9
4, 7, 12, 10, 17, 24, 13, 22, 31, 40, 16, 27, 38, 49, 60, 19, 32, 45, 58, 71, 84, 22, 37, 52, 67, 82, 97, 112, 25, 42, 59, 76, 93, 110, 127, 144, 28, 47, 66, 85, 104, 123, 142, 161, 180, 31, 52, 73, 94, 115, 136, 157, 178, 199, 220, 34, 57, 80, 103, 126, 149, 172, 195, 218, 241, 264 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

T(r,c) gives number of edges (of unit length) in a c X r grid.

The values 2*T(r,c)+1 = (2*r+1)*(2*c+1) are nonprime and therefore in A047845.

LINKS

Vincenzo Librandi, Rows n = 1..100, flattened

OEIS Wiki, Odd composites

EXAMPLE

Triangle begins:

4,

7,12,

10,17,24,

13,22,31,40,

16,27,38,49,60,

...

MATHEMATICA

t[n_, k_]:= 2 n k + n + k; Table[t[n, k], {n, 10}, {k, n}]//Flatten (* Vincenzo Librandi, Jun 01 2014 *)

PROG

(MAGMA) [(2*n*k + n + k): k in [1..n], n in [1..11]]; // Vincenzo Librandi, Jun 01 2014

CROSSREFS

Cf. A082652, A083003. See A151890 for another version.

Sequence in context: A178939 A072732 A270684 * A253129 A249918 A158937

Adjacent sequences:  A083484 A083485 A083486 * A083488 A083489 A083490

KEYWORD

nonn,tabl

AUTHOR

Artemario Tadeu Medeiros da Silva (artemario(AT)uol.com.br), Jun 09 2003

EXTENSIONS

Edited by N. J. A. Sloane, Jul 23 2009

STATUS

approved

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Last modified August 18 18:17 EDT 2017. Contains 290733 sequences.