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A131424 Triangle read by rows: T(n,k) = prime(n) + prime(k) - 3, 1 <= k <= n. 3

%I

%S 1,2,3,4,5,7,6,7,9,11,10,11,13,15,19,12,13,15,17,21,23,16,17,19,21,25,

%T 27,31,18,19,21,23,27,29,33,35,22,23,25,27,31,33,37,39,43,28,29,31,33,

%U 37,39,43,45,49,55,30,31,33,35,39,41,45,47,51,57,59

%N Triangle read by rows: T(n,k) = prime(n) + prime(k) - 3, 1 <= k <= n.

%C Left border = A006093, (primes - 1): (1, 2, 4, 6, 10, 12, ...). Right border = A131426 (2*primes - 3): (1, 3, 7, 11, 19, 23, 31, ...). Row sums = A131425: (1, 5, 16, 33, 68, 101, 156, ...).

%H Andrew Howroyd, <a href="/A131424/b131424.txt">Table of n, a(n) for n = 1..1275</a> (first 50 rows)

%F Equals (A000012 * A127640) + (A127640 * A000012) - 3*A000012 as infinite lower triangular matrices.

%e First few rows of the triangle are:

%e 1;

%e 2, 3;

%e 4, 5, 7;

%e 6, 7, 9, 11;

%e 10, 11, 13, 15, 19;

%e 12, 13, 15, 17, 21, 23;

%e 16, 17, 19, 21, 25, 27, 31;

%e 18, 19, 21, 23, 27, 29, 33, 35;

%e 22, 23, 25, 27, 31, 33, 37, 39, 43;

%e ...

%o (PARI) T(n,k) = if(k<=n, prime(n) + prime(k) - 3, 0) \\ _Andrew Howroyd_, Sep 01 2018

%Y Row sums are A131425.

%Y Cf. A127640, A131426, A006093, A000040.

%K nonn,tabl

%O 1,2

%A _Gary W. Adamson_, Jul 10 2007

%E Name clarified and terms a(56) and beyond from _Andrew Howroyd_, Sep 01 2018

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Last modified October 1 11:59 EDT 2020. Contains 337443 sequences. (Running on oeis4.)