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Irregular triangle read by rows in which row n lists the positive values k such that there are no primes between k*n and k*(n + 1), or -1 if no such k exists.
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%I #27 Jan 19 2024 21:31:39

%S 1,1,2,1,4,2,1,3,4,1,2,3,2,4,2,9,1,1,6,2,3,2,7,3,5,2,6,1,6,7,10,1,3,4,

%T 2,4,5,1,2,5,1,2,3,8,1,7,1,2,2,3,5,4,7,11,3,4,2,3,1,2,10,1,4,9,1,2,6,

%U 1,4,15,4,6,2,5,8,1,2,3,4,1,3,2,3,5,8,3,5,2,4,7,2,5,1,3,12,1,2,2,4,7

%N Irregular triangle read by rows in which row n lists the positive values k such that there are no primes between k*n and k*(n + 1), or -1 if no such k exists.

%e Triangle begins:

%e 1;

%e 1;

%e 1;

%e 2;

%e 1;

%e 4;

%e 2;

%e 1, 3, 4;

%e 1;

%e 2;

%e 3;

%e 2, 4;

%e 2, 9;

%e 1;

%e 1, 6;

%e 2, 3;

%e 2, 7;

%e 3, 5;

%e 2, 6;

%e 1, 6, 7, 10;

%e 1, 3, 4;

%e 2;

%e 4, 5;

%e 1, 2, 5;

%e 1, 2, 3, 8.

%Y Cf. A068780, A047845, A110835, A278425.

%K nonn,tabf,easy

%O 1,3

%A _Juri-Stepan Gerasimov_, Nov 25 2023