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A257251
Square array A(row,col) = A083221(row,col+1) - A083221(row,col): the first differences of each row of array constructed from the sieve of Eratosthenes.
8
2, 2, 6, 2, 6, 20, 2, 6, 10, 42, 2, 6, 20, 28, 110, 2, 6, 10, 14, 22, 156, 2, 6, 20, 28, 44, 52, 272, 2, 6, 10, 14, 22, 26, 34, 342, 2, 6, 20, 28, 44, 52, 68, 76, 506, 2, 6, 10, 42, 66, 78, 102, 114, 138, 812, 2, 6, 20, 14, 22, 26, 34, 38, 46, 58, 930, 2, 6, 10, 42, 66, 78, 102, 114, 138, 174, 186, 1332
OFFSET
1,1
COMMENTS
The array is read by downwards antidiagonals as A(1,1), A(1,2), A(2,1), A(1,3), A(2,2), A(3,1), ...
FORMULA
A(row,col) = A083221(row,col+1) - A083221(row,col).
A(row,col) = 2*A257253(row,col).
EXAMPLE
The top left corner of the array:
2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6
20, 10, 20, 10, 20, 10, 20, 10, 20, 10, 20, 10, 20, 10, 20
42, 28, 14, 28, 14, 28, 42, 14, 42, 28, 14, 28, 14, 28, 42
110, 22, 44, 22, 44, 66, 22, 66, 44, 22, 44, 66, 66, 22, 66
156, 52, 26, 52, 78, 26, 78, 52, 26, 52, 78, 78, 26, 78, 52
272, 34, 68, 102, 34, 102, 68, 34, 68, 102, 102, 34, 102, 68, 34
342, 76, 114, 38, 114, 76, 38, 76, 114, 114, 38, 114, 76, 38, 114
506, 138, 46, 138, 92, 46, 92, 138, 138, 46, 138, 92, 46, 138, 92
812, 58, 174, 116, 58, 116, 174, 174, 58, 174, 116, 58, 174, 116, 174
930, 186, 124, 62, 124, 186, 186, 62, 186, 124, 62, 186, 124, 186, 248
1332, 148, 74, 148, 222, 222, 74, 222, 148, 74, 222, 148, 222, 296, 148
1640, 82, 164, 246, 246, 82, 246, 164, 82, 246, 164, 246, 328, 164, 82
1806, 172, 258, 258, 86, 258, 172, 86, 258, 172, 258, 344, 172, 86, 172
2162, 282, 282, 94, 282, 188, 94, 282, 188, 282, 376, 188, 94, 188, 94
2756, 318, 106, 318, 212, 106, 318, 212, 318, 424, 212, 106, 212, 106, 212
...
MATHEMATICA
lim = 13; Clear[row]; row[n_] := row[n] = Take[Prime[n]*Select[Range[lim^2], GCD[#*Prime[n], Product[Prime[i], {i, n-1}]] == 1&], lim] // Differences;
A[n_, k_] := row[n][[k]]; Table[A[n-k+1, k], {n, 1, lim-1}, {k, n, 1, -1}] // Flatten (* Jean-François Alcover, Mar 08 2016, after Michael De Vlieger in A083221 *)
PROG
(Scheme)
(define (A257251 n) (A257251bi (A002260 n) (A004736 n)))
(define (A257251bi row col) (- (A083221bi row (+ 1 col)) (A083221bi row col))) ;; Code for A083221bi given in A083221.
CROSSREFS
Transpose: A257252.
Column 1: A036689.
Row 4: 7 * A145011.
Cf. A083221, A257253 (same array but with terms divided by 2).
Cf. arrays A257255 and A257257, also A257513.
Sequence in context: A187564 A138061 A257257 * A068555 A167556 A221438
KEYWORD
nonn,tabl,look
AUTHOR
Antti Karttunen, Apr 19 2015
STATUS
approved