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

1,3

Links

Table of n, a(n) for n=1..78.

Example

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

Prog

(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

Crossrefs

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

Sequence in context: A134560 A127626 A245095 * A121440 A348016 A353092

Adjacent sequences: A154788 A154789 A154790 * A154792 A154793 A154794

Keyword

nonn,tabl

Author

Omar E. Pol, Jan 25 2009

Extensions

More terms from Michel Marcus, Feb 13 2014

Status

approved