A154791 - OEIS

%I #11 Dec 08 2015 08:56:17

%S 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,

%T 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,

%U 17,19,0,1,0,5,7,0,11,13,0,17,19,0,23

%N 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.

%e Triangle begins:

%e n ....... Pairs

%e 1 ..........0

%e 2 ........ 1,3

%e 3 ....... 1,0,5

%e 4 ...... 1,3,5,7

%e 5 ..... 0,3,0,7,0

%e 6 .... 1,0,5,7,0,11

%o (PARI) iscomp(n) = (n!=1) && !isprime(n);

%o 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;}

%o trgp(nn) = {for (n = 1, nn, v = vecp(n); for (k = 1, n, print1(v[k], ", ");); print(););} \\ _Michel Marcus_, Feb 13 2014

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

%K nonn,tabl

%O 1,3

%A _Omar E. Pol_, Jan 25 2009

%E More terms from _Michel Marcus_, Feb 13 2014