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A256507 Triangle read by rows, giving in triangle A256946 the positions of n-th's row terms in row n+1. 2
1, 4, 7, 1, 2, 5, 7, 8, 11, 12, 14, 1, 2, 3, 6, 7, 9, 11, 12, 13, 16, 17, 19, 20, 22, 23, 1, 2, 3, 4, 7, 8, 10, 11, 13, 14, 16, 17, 18, 19, 22, 23, 24, 26, 27, 28, 30, 31, 33, 34, 1, 2, 3, 4, 5, 8, 9, 10, 12, 13, 14, 16, 17, 19, 20, 22, 23, 24, 25, 26, 29 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A256946(n+1,T(n,k),k) = A256946(n,k), k = 1..n*(n+2);

T(n,k) = k for k = 1..n;

T(n,n+1) = n + 3;

T(n,n*(n+2)) = (n+2)^2 - 2.

LINKS

Reinhard Zumkeller, Rows n = 1..30 of triangle, flattened

EXAMPLE

.  n | T(n,*)             | A256946(n,*)

. ---+--------------------+--------------------------------------

.  1 | 1,4,7              | [1,            2,          3]

.  2 | 1,2,5,7,8,11,12,14 | [1,4,     5,   2,6,      7,3,   8]

.  3 | 1,2,3,6,7,9,11,... | [1,4,9,10,5,11,2,6,12,13,7,3,14,8,15] .

MATHEMATICA

row[n_] := (* row of A256946 *) row[n] = SortBy[Range[n(n+2)], If[IntegerQ[ Sqrt[#]], 0, N[FractionalPart[Sqrt[#]]]]&];

T[n_, k_] := FirstPosition[row[n+1], row[n][[k]]][[1]];

Table[T[n, k], {n, 1, 5}, {k, 1, n(n+2)}] // Flatten (* Jean-Fran├žois Alcover, Sep 17 2019 *)

PROG

(Haskell)

import Data.List (elemIndex); import Data.Maybe (fromJust)

a256507 n k = a256507_tabf !! (n-1) !! (k-1)

a256507_row n = a256507_tabf !! (n-1)

a256507_tabf = zipWith (\us vs ->

                       map ((+ 1) . fromJust . (`elemIndex` vs)) us)

                       a256946_tabf $ tail a256946_tabf

CROSSREFS

Cf. A005563 (row lengths), A256946.

Sequence in context: A254338 A197723 A186191 * A123734 A011519 A131594

Adjacent sequences:  A256504 A256505 A256506 * A256508 A256509 A256510

KEYWORD

nonn,tabf

AUTHOR

Reinhard Zumkeller, Apr 22 2015

STATUS

approved

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Last modified November 15 01:07 EST 2019. Contains 329142 sequences. (Running on oeis4.)