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A337767
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Array T(n,k) (n >= 1, k >= 1) read by upward antidiagonals and defined as follows. Let N(p,i) denote the result of applying "nextprime" i times to p; T(n,k) = smallest prime p such that N(p,n) - p = 2*k, or 0 if no such prime exists.
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3
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3, 0, 7, 0, 3, 23, 0, 0, 5, 89, 0, 0, 0, 23, 139, 0, 0, 0, 3, 19, 199, 0, 0, 0, 0, 7, 47, 113, 0, 0, 0, 0, 3, 17, 83, 1831, 0, 0, 0, 0, 0, 5, 23, 211, 523, 0, 0, 0, 0, 0, 0, 17, 43, 109, 887, 0, 0, 0, 0, 0, 0, 3, 13, 79, 317, 1129, 0, 0, 0, 0, 0, 0, 0, 7, 19, 107, 619, 1669
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OFFSET
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1,1
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COMMENTS
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The positive entries in each row and column are distinct.
Number of zeros right of 3 are 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 2, 1, 3, 3, 3, 6, 5, 5, 4, 6, ..., .
Number of zeros in the n-th row are 0, 1, 3, 4, 6, 7, 10, 13, 14, 17, 18, 20, 22, 25, 28, 30, 32, 36, 37, 40, 45, 47, 51, 52, 55, ..., .
The usual convention in the OEIS is to use -1 in the "escape clause" - that is, when "no such terms exists". It is probably too late to change this sequence, but it should not be cited as a role model for other sequences. - N. J. A. Sloane, Jan 19 2021
a(1416), a(1637), and a(1753) were provided by Brian Kehrig. - Martin Raab, Jun 28 2024
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LINKS
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FORMULA
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T(n,k) = 0 if prime(n+2)-5 <= 2k. A089038.
T(n,k) = 3 if prime(n+2) = 2k+6. A067076.
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EXAMPLE
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The initial rows of the array are:
3, 7, 23, 89, 139, 199, 113, 1831, 523, 887, 1129, 1669, 2477, 2971, 4297, ...
0, 3, 5, 23, 19, 47, 83, 211, 109, 317, 619, 199, 1373, 1123, 1627, 4751, ...
0, 0, 0, 3, 7, 17, 23, 43, 79, 107, 109, 113, 197, 199, 317, 509, ...
0, 0, 0, 0, 3, 5, 17, 13, 19, 47, 79, 73, 113, 109, 193, 317, ...
0, 0, 0, 0, 0, 0, 3, 7, 11, 17, 19, 43, 71, 73, 107, 191, ...
0, 0, 0, 0, 0, 0, 0, 3, 5, 11, 7, 13, 41, 31, 67, 107, ...
0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 5, 11, 13, 23, 47, ...
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 7, 29, ...
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 5, ...
The initial antidiagonals are:
[3]
[0, 7]
[0, 3, 23]
[0, 0, 5, 89]
[0, 0, 0, 23, 139]
[0, 0, 0, 3, 19, 199]
[0, 0, 0, 0, 7, 47, 113]
[0, 0, 0, 0, 3, 17, 83, 1831]
[0, 0, 0, 0, 0, 5, 23, 211, 523]
[0, 0, 0, 0, 0, 0, 17, 43, 109, 887]
[0, 0, 0, 0, 0, 0, 3, 13, 79, 317, 1129]
...
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MATHEMATICA
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t[r_, c_] := If[ 2c <= Prime[r + 2] - 5, 0, Block[{p = 3}, While[ NextPrime[p, r] != 2c + p && p < 52000000, p = NextPrime@ p]; If[p > 52000000, 0, p]]]; Table[ t[r -c +1, c], {r, 11}, {c, r}] // Flatten
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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Deleted a-file and b-file because entries were unreliable. - N. J. A. Sloane, Nov 01 2021
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STATUS
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approved
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