A154791 Triangle read by rows in which row n lists all the pairs of noncomposite numbers that are equidistant from n, with 0's inserted, as shown below in the example.

0, 1, 3, 1, 0, 5, 1, 3, 5, 7, 0, 3, 0, 7, 0, 1, 0, 5, 7, 0, 11, 1, 3, 0, 0, 0, 11, 13, 0, 3, 5, 0, 0, 11, 13, 0, 1, 0, 5, 7, 0, 11, 13, 0, 17, 1, 3, 0, 7, 0, 0, 13, 0, 17, 19, 0, 3, 5, 0, 0, 0, 0, 0, 17, 19, 0, 1, 0, 5, 7, 0, 11, 13, 0, 17, 19, 0, 23

Offset: 1

Author

Omar E. Pol, Jan 25 2009

Keywords

• nonn
• tabl

Examples

			Triangle begins:
n ....... Pairs
1 ..........0
2 ........ 1,3
3 ....... 1,0,5
4 ...... 1,3,5,7
5 ..... 0,3,0,7,0
6 .... 1,0,5,7,0,11
		

Crossrefs

Cf. A008578, A154720, A154721, A154722, A154723.

Programs

PARI

iscomp(n) = (n!=1) && !isprime(n);
vecp(n) = {v = vector(n, i, 2*i-1); for (i = 1, n\2, if (iscomp(v[i]) || iscomp(v[n-i+1]), v[i] = 0; v[n-i+1] = 0);); if ((n % 2), v[n\2+1] = 0); v;}
trgp(nn) = {for (n = 1, nn, v = vecp(n); for (k = 1, n, print1(v[k], ", ");); print(););} \\ Michel Marcus, Feb 13 2014

Extensions

More terms from Michel Marcus, Feb 13 2014