A292473 Square array read by antidiagonals downwards: A(n,k) = k-th prime p such that A001222(2^p-1) = n.
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
Examples
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.
Programs
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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 *)
Extensions
More terms from Michael De Vlieger, Sep 17 2017
Comments