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A292473
Square array read by antidiagonals downwards: A(n,k) = k-th prime p such that A001222(2^p-1) = n.
0
2, 3, 11, 5, 23, 29, 7, 37, 43, 157, 13, 41, 47, 173, 113, 17, 59, 53, 181, 151, 223, 19, 67, 71, 229, 163, 239
OFFSET
1,1
COMMENTS
A permutation of the prime numbers.
Is this the same as k-th prime p such that A001221(2^p-1) = n?
EXAMPLE
Array starts
2, 3, 5, 7, 13, 17, ....
11, 23, 37, 41, 59, 67, ....
29, 43, 47, 53, 71, 73, ....
157, 173, 181, 229, 233, 263, ....
113, 151, 163, 191, 251, 307, ....
223, 239, 359, 463, 587, 641, ....
....
A(2, 3) = 37, because the 3rd prime p such that 2^p-1 has 2 prime factors is 37, with 2^37-1 = 223 * 616318177.
MATHEMATICA
With[{s = Array[PrimeOmega[2^Prime@ # - 1] &, 50]}, Function[t, Function[u, Table[Prime@ u[[#, k]] &[n - k + 1], {n, Length@t}, {k, n, 1, -1}]]@ Map[PadRight[#, Length@ t] &, t]]@ Values@ KeySort@ PositionIndex@ s] // Flatten (* Michael De Vlieger, Sep 17 2017 *)
CROSSREFS
Cf. A000043 (row 1), A135978 (row 2), A140745 (column 1).
Sequence in context: A333200 A229607 A137332 * A269253 A084047 A354585
KEYWORD
nonn,tabl,hard,more
AUTHOR
Felix Fröhlich, Sep 17 2017
EXTENSIONS
More terms from Michael De Vlieger, Sep 17 2017
STATUS
approved