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A260689 Table read by rows: numbers m such that (2*n-m, 2*n+m) is a prime pair. 6
1, 1, 3, 5, 3, 7, 1, 5, 7, 3, 9, 3, 13, 1, 5, 11, 13, 3, 9, 17, 9, 15, 19, 5, 7, 13, 17, 19, 3, 15, 21, 9, 15, 25, 1, 7, 11, 13, 17, 23, 9, 15, 21, 27, 29, 3, 27, 5, 7, 17, 23, 25, 31, 9, 15, 21, 33, 35, 3, 21, 27, 33, 1, 5, 11, 19, 25, 29, 31, 37, 3, 15, 27 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,3

COMMENTS

1 <= T(n,k) <= 2*n-3; T(n,2) > 3 for n > 3; all terms are odd;

A264526(n) = T(n,1);

A264527(n) = T(n,A069360(n));

T(A040040(n),1) = 1;

T(A088763(n),1) = 3.

LINKS

Reinhard Zumkeller, Rows n = 2..1000 of triangle, flattened

Index entries for sequences related to Goldbach conjecture

EXAMPLE

.   n | T(n,k)          | (2*n-T(n,k), 2*n+T(n,k))       k=1..A069360(n)

. ----+-----------------+-----------------------------------------------

.   2 | 1               | (3,5)

.   3 | 1               | (5,7)

.   4 | 3,5             | (5,11) (3,13)

.   5 | 3,7             | (7,13) (3,17)

.   6 | 1,5,7           | (11,13) (7,17) (5,19)

.   7 | 3,9             | (11,17) (5,23)

.   8 | 3,13            | (13,19) (3,29)

.   9 | 1,5,11,13       | (17,19) (13,23) (7,29) (5,31)

.  10 | 3,9,17          | (17,23) (11,29) (3,37)

.  11 | 9,15,19         | (13,31) (7,37) (3,41)

.  12 | 5,7,13,17,19    | (19,29) (17,31) (11,37) (7,41) (5,43)

.  13 | 3,15,21         | (23,29) (11,41) (5,47)

.  14 | 9,15,25         | (19,37) (13,43) (3,53)

.  15 | 1,7,11,13,17,23 | (29,31) (23,37) (19,41) (17,43) (13,47) (7,53)

.  16 | 9,15,21,27,29   | (23,41) (17,47) (11,53) (5,59) (3,61)

.  17 | 3,27            | (31,37) (7,61)

.  18 | 5,7,17,23,25,31 | (31,41) (29,43) (19,53) (13,59) (11,61) (5,67)

.  19 | 9,15,21,33,35   | (29,47) (23,53) (17,59) (5,71) (3,73)

.  20 | 3,21,27,33      | (37,43) (19,61) (13,67) (7,73) .

PROG

(Haskell)

a260689 n k = a260689_tabf !! (n-2) !! (k-1)

a260689_row n = [m | m <- [1, 3 .. 2 * n - 3],

                     a010051' (2*n + m) == 1, a010051' (2*n - m) == 1]

a260689_tabf = map a260689_row [2..]

CROSSREFS

Cf. A069360 (row lengths), A010051, A264526, A264527.

Sequence in context: A299418 A214456 A118271 * A328386 A095366 A029604

Adjacent sequences:  A260686 A260687 A260688 * A260690 A260691 A260692

KEYWORD

nonn,tabf

AUTHOR

Reinhard Zumkeller, Nov 17 2015

STATUS

approved

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Last modified March 8 20:52 EST 2021. Contains 341953 sequences. (Running on oeis4.)