A155546 Triangle read by rows where T(m,n)=2mn + m + n - 5, 1<=n<=m.

-1, 2, 7, 5, 12, 19, 8, 17, 26, 35, 11, 22, 33, 44, 55, 14, 27, 40, 53, 66, 79, 17, 32, 47, 62, 77, 92, 107, 20, 37, 54, 71, 88, 105, 122, 139, 23, 42, 61, 80, 99, 118, 137, 156, 175, 26, 47, 68, 89, 110, 131, 152, 173, 194, 215, 29, 52, 75, 98, 121, 144, 167, 190, 213

Offset: 1

Author

Vincenzo Librandi, Jan 24 2009

Keywords

• tabl
• sign
• easy

Comments

2*T(m,n)+11 = (2*m+1)*(2*n+1) is not prime.

First column: A016789, second column: A016873, third column: A017041, fourth column: A017257. - Vincenzo Librandi, Nov 21 2012

Examples

			Triangle begins:
-1;
2,  7;
5,  12, 19;
8,  17, 26, 35;
11, 22, 33, 44, 55;
14, 27, 40, 53, 66,  79;
17, 32, 47, 62, 77,  92,  107;
20, 37, 54, 71, 88,  105, 122, 139;
23, 42, 61, 80, 99,  118, 137, 156, 175;
26, 47, 68, 89, 110, 131, 152, 173, 194, 215; etc.
		

Links

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

Crossrefs

Cf. A101448, A153083, A016789, A016873, A017041, A017257.

Programs

Magma

[2*n*k + n + k - 5: k in [1..n], n in [1..11]]; // Vincenzo Librandi, Nov 21 2012

Mathematica

t[n_,k_]:= 2 n*k + n + k - 5; Table[t[n, k], {n, 15}, {k, n}]//Flatten (* Vincenzo Librandi, Nov 21 2012 *)