A173825 List of numbers k such that k=6*r+1=m*q, m>=q and n>=g where number m is 6*n+1 or 6*n-1 and number q is 6*g+1 or 6*g-1.

1, 7, 25, 49, 13, 55, 91, 121, 169, 19, 85, 133, 187, 247, 289, 361, 25, 115, 175, 253, 325, 391, 475, 529, 625, 31, 145, 217, 319, 403, 493, 589, 667, 775, 841, 961, 37, 175, 259, 385, 481, 595, 703, 805, 925, 1015, 1147, 1225, 1369, 43, 205, 301, 451, 559, 697

Offset: 1

Author

Juri-Stepan Gerasimov, Feb 26 2010

Keywords

• nonn

Comments

Triangle begins:

1 (for row n=0)

7 25 49 (for row n=1)

13 55 91 121 169 (for row n=2)

19 85 133 187 247 289 361 (for row n=3)

25 115 175 253 325 391 475 529 625 (for row n=4)

31 145 217 319 403 493 589 667 775 841 961 (for row n=5)

Examples

			a(1)=1 because 1=6*0+1=1*1=(6*0+1)*(6*0+1);
a(2)=7 because 7=6*1+1=7*1=(6*1+1)*(6*0+1);
a(3)=25 because 25=6*4+1=5*5=(6*1-1)*(6*1-1);
a(4)=49 because 49=6*8+1=7*7=(6*1+1)*(6*1+1);
a(5)=13 because 13=13*1=(6*2+1)*(6*0+1);
a(6)=55 because 55=6*9+1=11*5=(6*2-1)*(6*1-1);
a(7)=91 because 91=13*7=(6*2+1)*(6*1+1);
a(8)=121 because 121=6*20+1=11*11=(6*2-1)*(6*2-1);
a(9)=169 because 169=6*28+1=13+13=(6*2+1)*(6*2+1);
a(10)=19 because 19=6*3+1=19*1=(6*3+1)*(6*0+1).
		

Crossrefs

Cf. A007310.

Extensions

Entries checked by R. J. Mathar, Apr 14 2010