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 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. 1
 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 (list; table; graph; refs; listen; history; text; internal format)
 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

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Last modified July 21 20:59 EDT 2024. Contains 374475 sequences. (Running on oeis4.)