A255427 -id:A255427 - cp's OEIS frontend

A060265 Largest prime less than 2n.

3, 5, 7, 7, 11, 13, 13, 17, 19, 19, 23, 23, 23, 29, 31, 31, 31, 37, 37, 41, 43, 43, 47, 47, 47, 53, 53, 53, 59, 61, 61, 61, 67, 67, 71, 73, 73, 73, 79, 79, 83, 83, 83, 89, 89, 89, 89, 97, 97, 101, 103, 103, 107, 109, 109, 113, 113, 113, 113, 113, 113, 113, 127, 127, 131

Offset: 2

Labos Elemer, Mar 23 2001

a(n) = A007917(2*n) = A255313(n-1,1) = A255316(n-1,1) = A006530(A255427(n)). - Reinhard Zumkeller, Feb 22 2015

Harry J. Smith, Table of n, a(n) for n = 2..1000

Apart from initial term, same as A060308.

Cf. A020482, A049653, A088631, A007917, A005843, A255313.

a060265 = a007917 . (* 2)  -- Reinhard Zumkeller, Feb 22 2015

Maple
```
seq (prevprime(2*i+1), i=2..256);
```

Table[NextPrime[2 n, -1], {n, 2, 66}] (* Michael De Vlieger, Jul 04 2016 *)

a(n) = precprime(2*n-1) \\ Harry J. Smith, Jul 03 2009

A255316 Distinct terms in triangle A255313, table read by rows.

Original entry on oeis.org

3, 3, 5, 3, 5, 7, 5, 7, 5, 7, 11, 5, 7, 11, 13, 3, 5, 7, 11, 13, 3, 5, 7, 11, 13, 17, 3, 5, 7, 11, 13, 17, 19, 5, 7, 11, 13, 17, 19, 5, 7, 11, 13, 17, 19, 23, 5, 7, 11, 13, 17, 19, 23, 3, 7, 11, 13, 17, 19, 23, 3, 7, 11, 13, 17, 19, 23, 29, 3, 7, 11, 13, 17

Offset: 1

Reinhard Zumkeller, Feb 22 2015

			See A255313.

Reinhard Zumkeller, Rows n = 1..150 of triangle, flattened

Cf. A255313, A255395 (row lengths), A255427 (row products).

import Data.List (nub, sort)
a255316 n k = a255316_tabf !! (n-1) !! (k-1)
a255316_row n = a255316_tabf !! (n-1)
a255316_tabf = map (sort . nub) a255313_tabl

(* A is A088643 *)
A[n_, 1] := n;
A[n_, k_] := A[n, k] = For[m = n - 1, m >= 1, m--,
     If[PrimeQ[m + A[n, k - 1]] &&
     FreeQ[Table[A[n, j], {j, 1, k - 1}], m], Return[m]]];
T[n_] := T[n] = Union[2 MovingAverage[
     Table[A[n+1, k], {k, 1, n+1}], {1, 1}]];
Array[T, 20] // Flatten (* Jean-François Alcover, Aug 02 2021 *)

A255395 Number of distinct terms in row n of A255313.

Original entry on oeis.org

1, 2, 3, 2, 3, 4, 5, 6, 7, 6, 7, 7, 7, 8, 9, 9, 9, 10, 10, 11, 12, 12, 13, 13, 13, 14, 13, 13, 14, 15, 15, 16, 17, 17, 18, 19, 19, 18, 19, 19, 20, 21, 20, 21, 22, 22, 21, 22, 22, 23, 24, 24, 25, 26, 26, 27, 27, 28, 27, 26, 25, 26, 27, 24, 25, 26, 26, 27, 28

Offset: 1

Reinhard Zumkeller, Feb 22 2015

nonn

Row lengths for table A255316;

a(n) = A001221(A255427(n)) = A001222(A255427(n)).

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Cf. A255313, A255316, A255427.

import Data.List (nub)
a255395 = length . nub . a255313_row

cp's OEIS Frontend

A060265 Largest prime less than 2n.

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A255316 Distinct terms in triangle A255313, table read by rows.

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Mathematica

A255395 Number of distinct terms in row n of A255313.

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Haskell