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 A144562 Triangle read by rows: T(n, k) = 2*n*k + n + k - 1. 34
 3, 6, 11, 9, 16, 23, 12, 21, 30, 39, 15, 26, 37, 48, 59, 18, 31, 44, 57, 70, 83, 21, 36, 51, 66, 81, 96, 111, 24, 41, 58, 75, 92, 109, 126, 143, 27, 46, 65, 84, 103, 122, 141, 160, 179, 30, 51, 72, 93, 114, 135, 156, 177, 198, 219, 33, 56, 79, 102, 125, 148, 171, 194, 217, 240, 263 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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). LINKS Vincenzo Librandi, Rows n = 1..100, flattened Mutsumi Suzuki Vincenzo Librandi's method for sequential primes (Librandi's description in Italian). FORMULA Sum_{k=1..n} T(n,k) = n*(2*n^2 + 5*n - 1)/2 = A144640(n). - G. C. Greubel, Mar 01 2021 EXAMPLE Triangle begins: 3; 6, 11; 9, 16, 23; 12, 21, 30, 39; 15, 26, 37, 48, 59; 18, 31, 44, 57, 70, 83; 21, 36, 51, 66, 81, 96, 111; 24, 41, 58, 75, 92, 109, 126, 143; 27, 46, 65, 84, 103, 122, 141, 160, 179; MAPLE A144562:= (n, k) -> 2*n*k +n +k -1; seq(seq(A144562(n, k), k=1..n), n=1..12); # G. C. Greubel, Mar 01 2021 MATHEMATICA T[n_, k_]:= 2*n*k +n +k -1; Table[T[n, k], {n, 11}, {k, n}]//Flatten PROG (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 (PARI) T(n, k)=2*n*k+n+k-1 \\ Charles R Greathouse IV, Dec 28 2011 (Sage) flatten([[2*n*k+n+n-1 for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Mar 01 2021 CROSSREFS Cf. A067076, A142463, A144640, A153238. Sequence in context: A006509 A325551 A258928 * A102889 A183543 A256108 Adjacent sequences: A144559 A144560 A144561 * A144563 A144564 A144565 KEYWORD nonn,easy,tabl AUTHOR Vincenzo Librandi, Jan 06 2009 EXTENSIONS Edited by Ray Chandler, Jan 07 2009 STATUS approved

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Last modified February 26 17:57 EST 2024. Contains 370352 sequences. (Running on oeis4.)