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

1,1

Comments

A permutation of the prime numbers.

Is this the same as k-th prime p such that A001221(2^p-1) = n?

Links

Table of n, a(n) for n=1..27.

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).

Cf. A001222, A088863.

Sequence in context: A333200 A229607 A137332 * A269253 A084047 A354585

Adjacent sequences: A292470 A292471 A292472 * A292474 A292475 A292476

Keyword

nonn,tabl,hard,more

Author

Felix Fröhlich, Sep 17 2017

Extensions

More terms from Michael De Vlieger, Sep 17 2017

Status

approved