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A144562 Triangle read by rows: T(n, k) = 2nk + n + k - 1. 34

%I

%S 3,6,11,9,16,23,12,21,30,39,15,26,37,48,59,18,31,44,57,70,83,21,36,51,

%T 66,81,96,111,24,41,58,75,92,109,126,143,27,46,65,84,103,122,141,160,

%U 179,30,51,72,93,114,135,156,177,198,219,33,56,79,102,125,148,171,194

%N Triangle read by rows: T(n, k) = 2nk + n + k - 1.

%C Rearrangement of A153238, numbers n such that 2*n+3 is not prime (we have 2*T(n,k)+3=(2*n+1)*(2*k+1), as 2*n+3 is odd it consists of (at least) two odd factors and all such factors appear by definition).

%H Vincenzo Librandi, <a href="/A144562/b144562.txt">Rows n = 1..100, flattened</a>

%H Mutsumi Suzuki <a href="http://mathforum.org/te/exchange/hosted/suzuki/Vincent.html">Vincenzo Librandi's method for sequential primes</a> (Librandi's description in Italian).

%e Triangle begins:

%e 3;

%e 6, 11;

%e 9, 16, 23;

%e 12, 21, 30, 39;

%e 15, 26, 37, 48, 59;

%e 18, 31, 44, 57, 70, 83;

%e 21, 36, 51, 66, 81, 96, 111;

%e 24, 41, 58, 75, 92, 109, 126, 143;

%e 27, 46, 65, 84, 103, 122, 141, 160, 179;

%t t[n_, k_] := 2 n*k + n + k - 1; Table[t[n, k], {n, 11}, {k, n}] // Flatten

%o (MAGMA) [2*n*k+n+k-1: k in [1..n], n in [1..11]]; /* or, see example: */ [[2*n*k+n+k-1: k in [1..n]]: n in [1..9]]; // Bruno Berselli, Dec 04 2011

%o (PARI) T(n,k)=2*n*k+n+k-1 \\ _Charles R Greathouse IV_, Dec 28 2011

%Y Cf. A067076, A153238.

%K nonn,easy,tabl

%O 1,1

%A _Vincenzo Librandi_, Jan 06 2009

%E Edited by _Ray Chandler_, Jan 07 2009

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Last modified July 5 00:01 EDT 2020. Contains 335457 sequences. (Running on oeis4.)